Methanol and ethanol production for an oxygenate to olefin reaction system

ABSTRACT

The present invention provides various processes for producing light olefins from methanol and ethanol, optionally in a mixed alcohol stream. In one embodiment, the invention includes directing a first syngas stream to a methanol synthesis zone to form methanol and directing a second syngas stream and methanol to a homologation zone to form ethanol. The methanol and ethanol are directed to an oxygenate to olefin reaction system for conversion thereof to ethylene and propylene.

FIELD OF THE INVENTION

The present invention relates to processes for forming light olefins.More particularly, the present invention relates to processes forforming light olefins from a mixed alcohol feedstock.

BACKGROUND OF THE INVENTION

Light olefins, defined herein as ethylene and propylene, are importantcommodity petrochemicals useful in a variety of processes for makingplastics and other chemical compounds. Ethylene is used to make variouspolyethylene plastics, and in making other chemicals vinyl chloride,ethylene oxide, ethyl benzene and alcohol. Propylene is used to makevarious polypropylene plastics, and in making other chemicals such asacrylonitrile and propylene oxide.

The petrochemical industry has known for some time that oxygenates,especially alcohols, are convertible into light olefins. The preferredconversion process is generally referred to as an oxygenate to olefin(OTO) reaction process. Specifically, in an OTO reaction process, anoxygenate contacts a molecular sieve catalyst composition underconditions effective to convert at least a portion of the oxygenate tolight olefins. When methanol is the oxygenate, the process is generallyreferred to as a methanol to olefin (MTO) reaction process. Methanol isa particularly preferred oxygenate for the synthesis of ethylene and/orpropylene.

Depending on the respective commercial markets for ethylene andpropylene, it may be desirable to vary the weight ratio of ethylene topropylene formed in an OTO reaction system. It has recently beendiscovered, however, that although percent conversion may vary with achange in reaction conditions, e.g., temperature or pressure, theselectivity of a methanol-containing feedstock for ethylene andpropylene in an OTO reaction system generally remains constant withchanges in reaction conditions. Thus, the need exists in the art for aprocess for varying the ratio of ethylene to propylene formed in an OTOreaction system.

SUMMARY OF THE INVENTION

This invention provides processes for forming ethylene and propylenefrom an alcohol-containing feedstock comprising methanol and ethanol.The methanol in the alcohol-containing feedstock is formed in a processfor converting syngas to methanol in the presence of a catalystcomposition, while the ethanol in the alcohol-containing feedstock isformed from a homologation reaction of methanol with carbon monoxide andoptionally hydrogen. The alcohol-containing feedstock is directed to anoxygenate to olefin (OTO) reaction system for the conversion thereof toethylene and propylene. The resulting weight ratio of ethylene topropylene formed in the OTO reaction system advantageously can be variedby varying the weight ratio of the methanol to ethanol in thealcohol-containing feedstock that is directed to OTO reaction system orby modifying reaction conditions, e.g., temperature.

In one embodiment, the present invention is directed to a process forproducing light olefins. The process includes a step of contactingsyngas in the presence of one or more metal containing catalysts toproduce a first feedstock comprising methanol. A portion of the methanolis converted in a homologation zone to a second feedstock comprisingethanol. The first feedstock and the second feedstock are introduced toa process for converting the methanol and the ethanol in the presence ofa molecular sieve catalyst composition to the light olefins. Optionally,the second feedstock further comprises methanol. Preferably, the firstfeedstock and the second feedstock are combined to form a combinedfeedstock prior to the introduction of the first feedstock and thesecond feedstock to the process for converting the methanol and theethanol to the light olefins. In this embodiment, the combined feedstockcomprises methanol, ethanol and optionally water, the weight majority ofwhich preferably is removed from the combined feedstock prior to thestep that the first and second feedstocks are introduced to the processfor converting the methanol and the ethanol to the light olefins. Thecombined feedstock optionally further comprises light ends whichcomprise carbon monoxide, methane and hydrogen. In this embodiment, thelight ends preferably are removed from at least a portion of thecombined feedstock. The combined feedstock optionally has a methanol toethanol weight ratio of from about 4.0:1.0 to about 99.0:1.0, or morepreferably from about 9.0:1.0 to about 19.0:1.0. Preferably, the step ofconverting a portion of the methanol to a second feedstock comprisescontacting the portion of the methanol with a homologation catalystselected from the group consisting of: potassium oxides,cobalt-molybdenum sulfides, nickel-molybdenum sulfides and potassiumcarbonates. The converting step also preferably comprises contacting theportion of the methanol with the homologation catalyst in the presenceof carbon monoxide, optionally hydrogen and optionally carbon dioxide.Carbon monoxide preferably is produced in the conversion of the methanoland the ethanol to the light olefins. The produced carbon monoxideoptionally is separated from the light olefins and is directed to thehomologation zone to provide a carbon monoxide source for the step ofconverting the methanol to the second feedstock. Optionally, the one ormore metal-containing catalysts comprises one or more of carbon oxides,zinc oxides and aluminum oxides. Additionally, the process optionallycomprises the step of contacting a natural gas stream with oxygen underconditions effective to convert the natural gas stream into the syngas.

In another embodiment, the invention is directed to an integratedprocess for producing light olefins. This inventive process includes astep of contacting syngas with one or more metal-containing catalysts toproduce a first feedstock comprising methanol. A portion of the methanolpreferably contacts carbon monoxide in the presence of a catalyst systemto produce a second feedstock comprising ethanol. The first feedstockand the second feedstock, optionally in a combined stream, areintroduced to a process for converting the methanol and the ethanol inthe presence of a molecular sieve catalyst composition to the lightolefins.

In another embodiment, the invention is directed to a process forproducing light olefins, which includes a step of contacting a syngasstream with a methanol synthesis catalyst under first conditionseffective to form a methanol-containing stream comprising methanol. Atleast a portion of the methanol-containing stream contacts carbonmonoxide and a homologation catalyst under second conditions effectiveto form a mixed alcohol stream comprising methanol and ethanol. At leasta portion of the mixed alcohol stream contacts a molecular sievecatalyst composition under third conditions effective to convert themethanol and the ethanol to the light olefins. Optionally, the mixedalcohol stream further comprises water and the process further comprisesthe step of separating a weight majority of the water from the mixedalcohol stream. The second conditions optionally comprise a holomogationreaction temperature of from about 204° C. to about 316° C. Optionally,the process further comprises a step of separating the mixed alcoholstream into a first fraction and a second fraction. The first fractioncomprises a weight majority of the methanol present in the mixed alcoholstream, and the second fraction comprises a weight majority of theethanol present in the mixed alcohol stream.

Another embodiment of the present invention is directed to a process forproducing alcohols. In this embodiment, the invention includes a step ofcontacting a first syngas stream comprising carbon monoxide and hydrogenwith a methanol synthesis catalyst in a methanol synthesis zone underfirst conditions effective to form a methanol-containing streamcomprising hydrogen, carbon monoxide, methanol and water. A secondsyngas stream comprising carbon monoxide and optionally hydrogencontacts a methanol-containing feed stream and a homologation catalystin a homologation zone under second conditions effective to form anethanol-containing stream comprising carbon monoxide, methanol, ethanol,water and optionally hydrogen. At least a portion of themethanol-containing stream is combined with at least a portion of theethanol-containing stream to form a combined stream. At least a portionof the combined stream is separated in a light ends removal unit into afirst fraction and a second fraction. The first fraction comprises aweight majority of the hydrogen and carbon monoxide present in the atleast a portion of the combined stream. The second fraction comprises aweight majority of the methanol, ethanol, and water present in the atleast a portion of the combined stream. Water is removed from at least aportion of the second fraction in a water removal unit to form a thirdfraction and a fourth fraction. The third fraction comprises a weightmajority of the methanol and ethanol present in the at least a portionof the second fraction. The fourth fraction comprises a weight majorityof the water present in the at least a portion of the second fraction.The third fraction is separated into the methanol-containing feed streamand a final product stream, wherein the final product stream comprisesmethanol and ethanol. Optionally, the methanol-containing feed streamand the final product stream are aliquot portions of the third fraction,and the methanol-containing feed stream comprises methanol and ethanol.Optionally, this inventive process further comprises a step ofcontacting at least a portion of the final product stream with amolecular sieve catalyst composition under third conditions effective toconvert the methanol and ethanol to light olefins. Optionally, theprocess further includes a step of separating the final mixed alcoholstream into a fifth fraction and a sixth fraction. The fifth fractioncomprises a weight majority of the methanol present in the final mixedalcohol stream, and the sixth fraction comprises a weight majority ofthe ethanol present in the final mixed alcohol stream. Optionally, atleast a portion of the fifth fraction contacts a molecular sievecatalyst composition under third conditions effective to convert themethanol contained therein into light olefins. Additionally oralternatively, at least a portion of the sixth fraction contacts amolecular sieve catalyst composition under third conditions effective toconvert the ethanol contained therein to light olefins. Preferably, thestep of contacting at a least a portion of the sixth fraction with amolecular sieve catalyst composition occurs in a fixed bed reactionsystem.

In another embodiment, the invention is directed to a process forproducing light olefins. This process comprises a step of contacting asyngas stream comprising carbon monoxide, hydrogen and optionally carbondioxide with a methanol synthesis catalyst under first conditionseffective to form a methanol-containing stream comprising methanol andwater. At least a portion of the methanol-containing stream contactscarbon monoxide, optionally hydrogen and a homologation catalyst undersecond conditions effective to form a mixed alcohol stream comprisingmethanol, ethanol, and water. At least a portion of the mixed alcoholstream contacts a molecular sieve catalyst composition in a reactionsystem under third conditions effective to convert the methanol andethanol to light olefins. An effluent stream is yielded from thereaction system and comprises an ethylene to propylene weight ratio fromabout 0.9:1.0 to about 2.2:1.0, preferably from about 1.1:1.0 to about1.4:1.0.

In one embodiment, the invention comprises a step of contacting a firstsyngas stream comprising carbon monoxide, hydrogen and optionally carbondioxide with a methanol synthesis catalyst in a methanol synthesis zoneunder first conditions effective to form a methanol-containing streamcomprising hydrogen, carbon monoxide, methanol and water. A secondsyngas stream comprising carbon monoxide and optionally hydrogencontacts a methanol-containing feed stream and a homologation catalystin a homologation zone under second conditions effective to form anethanol-containing stream comprising carbon monoxide, methanol, ethanol,water and optionally hydrogen. At least a portion of themethanol-containing stream is combined with at least a portion of theethanol-containing stream to form a combined stream. At least a portionof the carbon monoxide, water and hydrogen are removed from at least aportion of the combined stream to form a final mixed alcohol stream. Afirst portion of the final mixed alcohol stream is directed to thehomologation zone to serve as the methanol-containing feed stream. Asecond portion of the final mixed alcohol stream contacts a molecularsieve catalyst composition in a reaction system under third conditionseffective to convert the methanol and ethanol to light olefins. Aneffluent stream, which has an ethylene to propylene weight ratio of fromabout 0.9:1.0 to about 2.2:1.0, preferably from about 1.1:1.0 to about1.4:1.0, is yielded from the reaction system. The first portion of thefinal mixed alcohol stream and the second portion of the final mixedalcohol stream optionally are aliquot portions of the final mixedalcohol stream. The methanol-containing feed stream optionally comprisesmethanol and ethanol. Optionally, this inventive process furthercomprises a step of separating the final mixed alcohol stream into afirst fraction and a second fraction. The first fraction comprises aweight majority of the methanol present in the final mixed alcoholstream, and the second fraction comprises a weight majority of theethanol present in the final mixed alcohol stream. In this embodiment,the first portion of the final mixed alcohol stream optionally comprisesa first portion of the first fraction. Optionally, the reaction systemcomprises a fast-fluidized reaction zone and a fixed bed reaction zone.A second portion of the first fraction is directed to the fast fluidizedreaction zone for conversion of the methanol contained therein to lightolefins. At least a portion of the second fraction is directed to thefixed bed reaction system for the conversion of the ethanol containedtherein to light olefins.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be better understood by reference to the detaileddescription of the invention when taken together with the attacheddrawings, wherein:

FIG. 1 is a flow diagram of a methanol synthesis system;

FIG. 2 is a flow diagram of one embodiment of the present invention;

FIG. 3 is a flow diagram of another embodiment of the present invention;and

FIG. 4 is a flow diagram of another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A. Introduction

The present invention provides processes for forming analcohol-containing stream comprising both methanol and ethanol. Themethanol in the alcohol-containing stream is formed in a process forconverting syngas to methanol in the presence of a catalyst composition.The ethanol in the alcohol-containing stream is formed from ahomologation reaction of methanol with carbn monoxide and optionallyhydrogen in the presence of a homologation catalyst. Thealcohol-containing stream preferably is directed to an oxygenate toolefin (OTO) reaction system, wherein the methanol and ethanol containedin the alcohol-containing stream are converted to ethylene andpropylene. According to one preferred embodiment of the presentinvention, the resulting weight ratio of ethylene to propylene that isformed in the OTO reaction system can be varied by varying the weightratio of the methanol to ethanol contained in the alcohol-containingstream that is directed to the OTO reaction system, or by varyingreaction conditions, e.g., temperature. Thus, the present invention isdirected to an integrated system wherein methanol is synthesized in amethanol synthesis unit, and ethanol is synthesized in an ethanolsynthesis unit. Preferably the methanol and the ethanol are combined toform a combined stream, which is directed to an OTO reaction system forthe formation of ethylene and propylene. A detailed description ofmethanol synthesis systems will now be described.

B. Methanol Synthesis Systems

1. Examples of Methanol Synthesis Processes

There are numerous technologies available for producing methanolincluding fermentation or the reaction of synthesis gas (syngas) derivedfrom a hydrocarbon feed stream, which may include natural gas, petroleumliquids, carbonaceous materials including coal, recycled plastics,municipal waste or any other organic material. Methanol is typicallysynthesized from the catalytic reaction of syngas in a methanolsynthesis reactor in the presence of a heterogeneous catalyst. Forexample, in one synthesis process methanol is produced using acopper/zinc oxide catalyst in a water-cooled tubular methanol reactor.Syngas is defined as a gas comprising carbon monoxide (CO), preferablyhydrogen (H₂) and optionally carbon dioxide (CO₂). Optionally, syngasmay also include unreacted feedstocks such as methane (CH₄), ethane,propane, heavier hydrocarbons, or other compounds. Generally, theproduction of syngas involves a reforming reaction of natural gas,mostly methane, and an oxygen source into hydrogen, carbon monoxideand/or carbon dioxide. Syngas production processes are well known, andinclude conventional steam reforming, autothermal reforming, or acombination thereof.

Methanol compositions can be manufactured from a hydrocarbon feed streamderived from a variety of carbon sources. Examples of such sourcesinclude biomass, natural gas, C1–C5 hydrocarbons, naphtha, heavypetroleum oils, or coke (i.e., coal). Preferably, the hydrocarbon feedstream comprises methane in an amount of at least about 50% by volume,more preferably at least about 70% by volume, most preferably at leastabout 80% by volume. In one embodiment of this invention natural gas isthe preferred hydrocarbon feed source.

One way of converting the carbon source to a methanol composition is tofirst convert the carbon source to syngas, and then convert the syngasto the methanol composition. Any conventional process can be used. Inparticular, any conventional carbon oxide conversion catalyst can beused to convert the syngas to the methanol composition. In oneembodiment, the carbon oxide conversion catalyst is a nickel containingcatalyst.

The hydrocarbon feed stream that is used in the conversion ofhydrocarbon to syngas is optionally treated to remove impurities thatcan cause problems in further processing of the hydrocarbon feed stream.These impurities can poison many conventional propylene and ethyleneforming catalysts. A majority of the impurities that may be present canbe removed in any conventional manner. The hydrocarbon feed ispreferably purified to remove sulfur compounds, nitrogen compounds,particulate matter, other condensables, and/or other potential catalystpoisons prior to being converted into syngas.

In one embodiment of the invention, the hydrocarbon feed stream ispassed to a syngas plant. The syngas preferably has an appropriate molarratio of hydrogen to carbon oxide (carbon monoxide and/or carbondioxide), as described below. The syngas plant may employ anyconventional means of producing syngas, including partial oxidation,steam or CO₂ reforming, or a combination of these two chemistries.

Steam reforming generally comprises contacting a hydrocarbon with steamto form syngas. The process preferably includes the use of a catalyst.

Partial oxidation generally comprises contacting a hydrocarbon withoxygen or an oxygen-containing gas such as air to form syngas. Partialoxidation takes place with or without the use of a catalyst, althoughthe use of a catalyst is preferred. In one embodiment, water (steam) isadded with the feed in the partial oxidation process. Such an embodimentis generally referred to as autothermal reforming.

Conventional syngas-generating processes include gas phase partialoxidation, autothermal reforming, fluid bed syngas generation, catalyticpartial oxidation and various processes for steam reforming.

2. Steam Reforming to Make Syngas

In the catalytic steam reforming process, hydrocarbon feeds areconverted to a mixture of H₂, CO and CO₂ by reacting hydrocarbons withsteam over a catalyst. This process involves the following reactions:CH₄+H₂O⇄CO+3H₂  (1)orC_(n)H_(m)+nH₂O⇄nCO+[n+(m/2)]H₂ and  (2)CO+H₂O⇄CO₂+H₂ (shift reaction)  (3)

The reaction is carried out in the presence of a catalyst. Anyconventional reforming type catalyst can be used. The catalyst used inthe step of catalytic steam reforming comprises at least one activemetal or metal oxide of Group 6 or Group 8–10 of the Periodic Table ofthe Elements. The Periodic Table of the Elements referred to herein isthat from CRC Handbook of Chemistry and Physics, 82nd Edition,2001–2002, CRC Press LLC, which is incorporated herein by reference.

In one embodiment, the catalyst contains at least one Group 6 or Group8–10 metal, or oxide thereof, having an atomic number of 28 or greater.Specific examples of reforming catalysts that can be used are nickel,nickel oxide, cobalt oxide, chromia and molybdenum oxide. Optionally,the catalyst is employed with at least one promoter. Examples ofpromoters include alkali and rare earth promoters. Generally, promotednickel oxide catalysts are preferred.

The amount of Group 6 or Group 8–10 metals in the catalyst can vary.Preferably, the catalyst includes from about 3 wt % to about 40 wt % ofat least one Group 6 or Group 8–10 metal, based on total weight of thecatalyst. Preferably, the catalyst includes from about 5 wt % to about25 wt % of at least one Group 6 or Group 8–10 metal, based on totalweight of the catalyst.

The reforming catalyst optionally contains one or more metals tosuppress carbon deposition during steam reforming. Such metals areselected from the metals of Group 14 and Group 15 of the Periodic Tableof the Elements. Preferred Group 14 and Group 15 metals includegermanium, tin, lead, arsenic, antimony, and bismuth. Such metals arepreferably included in the catalyst in an amount of from about 0.1 wt %to about 30 wt %, based on total weight of nickel in the catalyst.

In a catalyst comprising nickel and/or cobalt there may also be presentone or more platinum group metals, which are capable of increasing theactivity of the nickel and/or cobalt and of decreasing the tendency tocarbon lay-down when reacting steam with hydrocarbons higher thanmethane. The concentration of such platinum group metal is typically inthe range 0.0005 to 0.1 weight percent metal, calculated as the wholecatalyst unit. Further, the catalyst, especially in preferred forms, cancontain a platinum group metal but no non-noble catalytic component.Such a catalyst is more suitable for the hydrocarbon steam reformingreaction than one containing a platinum group metal on a conventionalsupport because a greater fraction of the active metal is accessible tothe reacting gas. A typical content of platinum group metal when usedalone is in the range 0.0005 to 0.5% w/w as metal, calculated on thewhole catalytic unit.

In one embodiment, the reformer unit includes tubes which are packedwith solid catalyst granules. Preferably, the solid catalyst granulescomprise nickel or other catalytic agents deposited on a suitable inertcarrier material. More preferably, the catalyst is NiO supported oncalcium aluminate, alumina, spinel type magnesium aluminum oxide orcalcium aluminate titanate.

In yet another embodiment, both the hydrocarbon feed stream and thesteam are preheated prior to entering the reformer. The hydrocarbonfeedstock is preheated up to as high a temperature as is consistent withthe avoiding of undesired pyrolysis or other heat deterioration. Sincesteam reforming is endothermic in nature, and since there are practicallimits to the amount of heat that can be added by indirect heating inthe reforming zones, preheating of the feed is desired to facilitate theattainment and maintenance of a suitable temperature within the reformeritself. Accordingly, it is desirable to preheat both the hydrocarbonfeed and the steam to a temperature of at least 200° C.; preferably atleast 400° C. The reforming reaction is generally carried out at areformer temperature of from about 500° C. to about 1,200° C.,preferably from about 800° C. to about 1,100° C., and more preferablyfrom about 900° C. to about 1,050° C.

Gas hourly space velocity in the reformer should be sufficient forproviding the desired CO to CO₂ balance in the syngas. Preferably, thegas hourly space velocity (based on wet feed) is from about 3,000 perhour to about 10,000 per hour, more preferably from about 4,000 per hourto about 9,000 per hour, and most preferably from about 5,000 per hourto about 8,000 per hour.

Any conventional reformer can be used in the step of catalytic steamreforming. The use of a tubular reformer is preferred. Preferably, thehydrocarbon feed is passed to a tubular reformer together with steam,and the hydrocarbon and steam contact a steam reforming catalyst. In oneembodiment, the steam reforming catalyst is disposed in a plurality offurnace tubes that are maintained at an elevated temperature by radiantheat transfer and/or by contact with combustion gases. Fuel, such as aportion of the hydrocarbon feed, is burned in the reformer furnace toexternally heat the reformer tubes therein. See, for example,Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd Ed., 1990, vol.12, p. 951; and Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed.,1989, vol. A-12, p. 186, the relevant portions of each being fullyincorporated herein by reference.

The ratio of steam to hydrocarbon feed will vary depending on theoverall conditions in the reformer. The amount of steam employed isinfluenced by the requirement of avoiding carbon deposition on thecatalyst, and by the acceptable methane content of the effluent at thereforming conditions maintained. On this basis, the mole ratio of steamto hydrocarbon feed in the conventional primary reformer unit ispreferably from about 1.5:1 to about 5:1, preferably from about 2:1 toabout 4:1.

Typically, the syngas formed comprises hydrogen and a carbon oxide. Thehydrogen to carbon oxide ratio of the syngas produced will varydepending on the overall conditions of the reformer. Preferably, themolar ratio of hydrogen to carbon oxide in the syngas will range fromabout 1:1 to about 5:1. More preferably the molar ratio of hydrogen tocarbon oxide will range from about 2:1 to about 3:1. Even morepreferably the molar ratio of hydrogen to carbon oxide will range fromabout 2:1 to about 2.5:1. Most preferably the molar ration of hydrogento carbon oxide will range from about 2:1 to about 2.3:1.

Steam reforming is generally carried out at superatmospheric pressure.The specific operating pressure employed is influenced by the pressurerequirements of the subsequent process in which the reformed gas mixtureis to be employed. Although any superatmospheric pressure can be used inpracticing the invention, pressures of from about 175 psig (1,308 kPaabs.) to about 1,100 psig (7,686 kPa abs.) are desirable. Preferably,steam reforming is carried out at a pressure of from about 300 psig(2,170 kPa abs.) to about 800 psig (5,687 kPa abs.), more preferablyfrom about 350 psig (2,515 kPa abs.) to about 700 psig (4,928 kPa abs.).

3. Partial Oxidation to Make Syngas

The invention optionally provides for the production of syngas, or COand H₂, by oxidative conversion (also referred to herein as partialoxidation) of hydrocarbons, particularly natural gas and C₁–C₅hydrocarbons. According to the process, one or more hydrocarbons arereacted with free-oxygen to form CO and H₂. The process is carried outwith or without a catalyst. The use of a catalyst is preferred,preferably with the catalyst containing at least one non-transition ortransition metal oxides. The process is essentially exothermic, and isan incomplete combustion reaction, having the following general formula:C_(n)H_(m)+(n/2)O₂⇄nCO+(m/2)H₂  (4)

Non-catalytic partial oxidation of hydrocarbons to H₂, CO and CO₂ isdesirably used for producing syngas from heavy fuel oils, primarily inlocations where natural gas or lighter hydrocarbons, including naphtha,are unavailable or uneconomical compared to the use of fuel oil or crudeoil. The non-catalytic partial oxidation process is carried out byinjecting preheated hydrocarbon, oxygen and steam through a burner intoa closed combustion chamber. Preferably, the individual components areintroduced at a burner where they meet in a diffusion flame, producingoxidation products and heat. In the combustion chamber, partialoxidation of the hydrocarbons generally occurs with less thanstoichiometric oxygen at very high temperatures and pressures.Preferably, the components are preheated and pressurized to reducereaction time. The process preferably occurs at a temperature of fromabout 1,350° C. to about 1,600° C., and at a pressure of from aboveatmospheric to about 150 atm.

Catalytic partial oxidation comprises passing a gaseous hydrocarbonmixture, and oxygen, preferably in the form of air, over reduced orunreduced composite catalysts. The reaction is optionally accompanied bythe addition of water vapor (steam). When steam is added, the reactionis generally referred to as autothermal reduction. Autothermal reductionis both exothermic and endothermic as a result of adding both oxygen andwater.

In the partial oxidation process, the catalyst comprises at least onetransition element selected from the group consisting of Ni, Co, Pd, Ru,Rh, Ir, Pt, Os and Fe. Preferably, the catalyst comprises at least onetransition element selected from the group consisting of Pd, Pt, and Rh.In another embodiment, preferably the catalyst comprises at least onetransition element selected form the group consisting of Ru, Rh, and Ir.

In one embodiment, the partial oxidation catalyst further comprises atleast one metal selected from the group consisting of Ti, Zr, Hf, Y, Th,U, Zn, Cd, B, Al, Tl , Si, Sn, Pb, P, Sb, Bi, Mg, Ca, Sr, Ba, Ga, V, andSc. Also, optionally included in the partial oxidation catalyst is atleast one rare earth element selected from the group consisting of La,Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

In another embodiment the catalyst employed in the process may comprisea wide range of catalytically active components, for example Pd, Pt, Rh,Ir, Os, Ru, Ni, Cr, Co, Ce, La and mixtures thereof. Materials notnormally considered to be catalytically active may also be employed ascatalysts, for example refractory oxides such as cordierite, mullite,mullite aluminum titanate, zirconia spinels and alumina.

In yet another embodiment, the catalyst is comprised of metals selectedfrom those having atomic number 21 to 29, 40 to 47 and 72 to 79, themetals Sc, Ti V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag,Hf, Ta, W, Re, Os Ir, Pt, and Au. The preferred metals are those inGroup 8 of the Periodic Table of the Elements, that is Fe, Os, Co, Re,Ir, Pd, Pt, Ni, and Ru.

In another embodiment, the partial oxidation catalyst comprises at leastone transition or non-transition metal deposited on a monolith support.The monolith supports are preferably impregnated with a noble metal suchas Pt, Pd or Rh, or other transition metals such as Ni, Co, Cr and thelike. Desirably, these monolith supports are prepared from solidrefractory or ceramic materials such as alumina, zirconia, magnesia,ceria, silica, titania, mixtures thereof, and the like. Mixed refractoryoxides, that is refractory oxides comprising at least two cations, mayalso be employed as carrier materials for the catalyst.

In one embodiment, the catalyst is retained in form of a fixedarrangement. The fixed arrangement generally comprises a fixed bed ofcatalyst particles. Alternatively, the fixed arrangement comprises thecatalyst in the form of a monolith structure. The fixed arrangement mayconsist of a single monolith structure or, alternatively, may comprise anumber of separate monolith structures combined to form the fixedarrangement. A preferred monolith structure comprises a ceramic foam.Suitable ceramic foams for use in the process are availablecommercially.

In yet another embodiment, the feed comprises methane, and the feed isinjected with oxygen into the partial oxidation reformer at a methane tooxygen (i.e., O₂) ratio of from about 1.2:1 to about 10:1. Preferablythe feed and oxygen are injected into the reformer at a methane tooxygen ratio of from about 1.6:1 to about 8:1, more preferably fromabout 1.8:1 to about 4:1.

Water may or may not be added to the partial oxidation process. Whenadded, the concentration of water injected into the reformer is notgenerally greater than about 65 mole %, based on total hydrocarbon andwater feed content. Preferably, when water is added, it is added at awater to methane ratio of not greater than 3:1, preferably not greaterthan 2:1.

The catalyst may or may not be reduced before the catalytic reaction. Inone embodiment, the catalyst is reduced and reduction is carried out bypassing a gaseous mixture comprising hydrogen and inert gas (e.g., N₂,He, or Ar) over the catalyst in a fixed bed reactor at a catalystreduction pressure of from about 1 atm to about 5 atm, and a catalystreduction temperature of from about 300° C. to about 700° C. Hydrogengas is used as a reduction gas, preferably at a concentration of fromabout 1 mole % to about 100 mole %, based on total amount of reductiongas. Desirably, the reduction is further carried out at a space velocityof reducing gas mixture of from about 103 cm³/g·hr to about 105 cm³/g·hrfor a period of from about 0.5 hour to about 20 hours.

In one embodiment, the partial oxidation catalyst is not reduced byhydrogen. When the catalyst is not reduced by hydrogen before thecatalytic reaction, the reduction of the catalyst can be effected bypassing the hydrocarbon feed and oxygen (or air) over the catalyst attemperature in the range of from about 500° C. to about 900° C. for aperiod of from about 0.1 hour to about 10 hours.

In the partial oxidation process, carbon monoxide (CO) and hydrogen (H₂)are formed as major products, and water and carbon dioxide (CO₂) asminor products. The gaseous product stream comprises the above mentionedproducts, unconverted reactants (i.e. methane or natural gas and oxygen)and components of feed other than reactants.

When water is added in the feed, the H₂:CO mole ratio in the product isincreased by the shift reaction: CO+H₂O⇄H₂+CO₂. This reaction occurssimultaneously with the oxidative conversion of the hydrocarbon in thefeed to CO and H₂ or syngas. The hydrocarbon used as feed in the partialoxidation process is preferably in the gaseous phase when contacting thecatalyst. The partial oxidation process is particularly suitable for thepartial oxidation of methane, natural gas, associated gas or othersources of light hydrocarbons. In this respect, the term “lighthydrocarbons” is a reference to hydrocarbons having from 1 to 5 carbonatoms. The process may be advantageously applied in the conversion ofgas from naturally occurring reserves of methane which containsubstantial amounts of carbon dioxide. In one embodiment, thehydrocarbon feed preferably contains from about 10 mole % to about 90mole % methane, based on total feed content. More preferably, thehydrocarbon feed contains from about 20 mole % to about 80 mole %methane, based on total feed content. In another embodiment, the feedcomprises methane in an amount of at least 50% by volume, morepreferably at least 70% by volume, and most preferably at least 80% byvolume.

In one embodiment of the invention, the hydrocarbon feedstock iscontacted with the catalyst in a mixture with an oxygen-containing gas.Air is suitable for use as the oxygen-containing gas. Substantially pureoxygen as the oxygen-containing gas is preferred on occasions wherethere is a need to avoid handling large amounts of inert gas such asnitrogen. The feed optionally comprises steam.

In another embodiment of the invention, the hydrocarbon feedstock andthe oxygen-containing gas are preferably present in the feed in suchamounts as to give an oxygen-to-carbon ratio in the range of from about0.3:1 to about 0.8:1, more preferably, in the range of from about 0.45:1to about 0.75:1. References herein to the oxygen-to-carbon ratio referto the ratio of oxygen in the from of oxygen molecules (O₂) to carbonatoms present in the hydrocarbon feedstock. Preferably, theoxygen-to-carbon ratio is in the range of from about 0.45:1 to about0.65:1, with oxygen-to-carbon ratios in the region of the stoichiometricratio of 0.5:1, that is ratios in the range of from about 0.45:1 toabout 0.65:1, being more preferred. When steam is present in the feed,the steam-to-carbon ratio is not greater than about 3.0:1, morepreferably not greater than about 2.0:1. The hydrocarbon feedstock, theoxygen-containing gas and steam, if present, are preferably well mixedprior to being contacted with the catalyst.

The partial oxidation process is operable over a wide range ofpressures. For applications on a commercial scale, elevated pressures,that is pressures significantly above atmospheric pressure, arepreferred. In one embodiment, the partial oxidation process is operatedat pressures of greater than atmospheric up to about 150 bars.Preferably, the partial oxidation process is operated at a pressure inthe range of from about 2 bars to about 125 bars, more preferably fromabout 5 bars to about 100 bars.

The partial oxidation process is also operable over a wide range oftemperatures. At commercial scale, the feed is preferably contacted withthe catalyst at high temperatures. In one embodiment, the feed mixtureis contacted with the catalyst at a temperature in excess of 600° C.Preferably, the feed mixture is contacted with the catalyst at atemperature in the range of from about 600° C. to about 1,700° C., morepreferably from about 800° C. to about 1,600° C. The feed mixture ispreferably preheated prior to contacting the catalyst.

The feed is provided during the operation of the process at a suitablespace velocity to form a substantial amount of CO in the product. In oneembodiment, gas space velocities (expressed in normal liters of gas perkilogram of catalyst per hour) are in the range of from about 20,000Nl/kg/hr to about 100,000,000 Nl/kg/hr, more preferably in the range offrom about 50,000 Nl/kg/hr to about 50,000,000 Nl/kg/hr, and mostpreferably in the range of from about 500,000 Nl/kg/hr to about30,000,000 Nl/kg/hr.

4. Combination Syngas Processes

Combination reforming processes can also be incorporated into thisinvention. Examples of combination reforming processes includeautothermal reforming and fixed bed syngas generation. These processesinvolve a combination of gas phase partial oxidation and steam reformingchemistry.

The autothermal reforming process preferably comprises two syngasgenerating processes, a primary oxidation process and a secondary steamreforming process. In one embodiment, a hydrocarbon feed stream is steamreformed in a tubular primary reformer by contacting the hydrocarbon andsteam with a reforming catalyst to form a hydrogen and carbon monoxidecontaining primary reformed gas, the carbon monoxide content of which isfurther increased in the secondary reformer. In one embodiment, thesecondary reformer includes a cylindrical refractory lined vessel with agas mixer, preferably in the form of a burner in the inlet portion ofthe vessel and a bed of nickel catalyst in the lower portion. In a morepreferred embodiment, the exit gas from the primary reformer is mixedwith air and residual hydrocarbons, and the mixed gas partial oxidizedto carbon monoxides.

In another embodiment incorporating the autothermal reforming process,partial oxidation is carried out as the primary oxidating process.Preferably, hydrocarbon feed, oxygen, and optionally steam, are heatedand mixed at an outlet of a single large coaxial burner or injectorwhich discharges into a gas phase partial oxidation zone. Oxygen ispreferably supplied in an amount which is less than the amount requiredfor complete combustion.

Upon reaction in the partial oxidation combustion zone, the gases flowfrom the primary reforming process into the secondary reforming process.In one embodiment, the gases are passed over a bed of steam reformingcatalyst particles or a monolithic body, to complete steam reforming.Desirably, the entire hydrocarbon conversion is completed by a singlereactor aided by internal combustion.

In an alternative embodiment of the invention, a fixed bed syngasgeneration process is used to form syngas. In the fixed bed syngasgeneration process, hydrocarbon feed and oxygen or an oxygen-containinggas are introduced separately into a fluid catalyst bed. Preferably, thecatalyst is comprised of nickel and supported primarily on alphaalumina.

The fixed bed syngas generation process is carried out at conditions ofelevated temperatures and pressures that favor the formation of hydrogenand carbon monoxide when, for example, methane is reacted with oxygenand steam. Preferably, temperatures are in excess of about 1,700° F.(927° C.), but not so high as to cause disintegration of the catalyst orthe sticking of catalyst particles together. Preferably, temperaturesrange from about 1,750° F. (954° C.) to about 1,950° F. (1,066° C.),more preferably, from about 1,800° F. (982° C.) to about 1,850° F.(1,010° C.).

Pressure in the fixed bed syngas generation process may range fromatmospheric to about 40 atmospheres. In one embodiment, pressures offrom about 20 atmospheres to about 30 atmospheres are preferred, whichallows subsequent processes to proceed without intermediate compressionof product gases.

In one embodiment of the invention, methane, steam, and oxygen areintroduced into a fluid bed by separately injecting the methane andoxygen into the bed. Alternatively, each stream is diluted with steam asit enters the bed. Preferably, methane and steam are mixed at a methaneto steam molar ratio of from about 1:1 to about 3:1, and more preferablyfrom about 1.5:1 to about 2.5:1, and the methane and steam mixture isinjected into the bed. Preferably, the molar ratio of oxygen to methaneis from about 0.2:1 to about 1.0:1, more preferably from about 0.4:1 toabout 0.6:1.

In another embodiment of the invention, the fluid bed process is usedwith a nickel based catalyst supported on alpha alumina. In anotherembodiment, silica is included in the support. The support is preferablycomprised of at least 95 wt % alpha alumina, more preferably at leastabout 98% alpha alumina, based on total weight of the support.

In one embodiment, a gaseous mixture of hydrocarbon feedstock andoxygen-containing gas are contacted with a reforming catalyst underadiabatic conditions. For the purposes of this invention, the term“adiabatic” refers to reaction conditions in which substantially allheat loss and radiation from the reaction zone are prevented, with theexception of heat leaving in the gaseous effluent stream of the reactor.

5. Converting Syngas to Methanol

The syngas is sent to a methanol synthesis process and converted tomethanol. The methanol synthesis process is accomplished in the presenceof a methanol synthesis catalyst.

In one embodiment, the syngas is sent as is to the methanol synthesisprocess. In another embodiment, the hydrogen, carbon monoxide, and/orcarbon dioxide content of the syngas is adjusted for efficiency ofconversion. Desirably, the syngas input to the methanol synthesisreactor has a molar ratio of hydrogen (H₂) to carbon oxides (CO+CO₂) inthe range of from about 0.5:1 to about 20:1, preferably in the range offrom about 2:1 to about 10:1. In another embodiment, the syngas has amolar ratio of hydrogen (H₂) to carbon monoxide (CO) of at least 2:1.Carbon dioxide is optionally present in an amount of not greater than50% by weight, based on total weight of the syngas.

Desirably, the stoichiometric molar ratio is sufficiently high so asmaintain a high yield of methanol, but not so high as to reduce thevolume productivity of methanol. Preferably, the syngas fed to themethanol synthesis has a stoichiometric molar ratio (i.e., a molar ratioof H₂:(2CO+3CO₂)) of from about 1.0:1 to about 2.7:1, more preferablyfrom about 1.1 to about 2.0, more preferably a stoichiometric molarratio of from about 1.2:1 to about 1.8:1.

The CO₂ content, relative to that of CO, in the syngas should be highenough so as to maintain an appropriately high reaction temperature andto minimize the amount of undesirable by-products such as paraffins. Atthe same time, the relative CO₂ to CO content should not be too high soas to reduce methanol yield. Desirably, the syngas contains CO₂ and COat a molar ratio of from about 0.5 to about 1.2, preferably from about0.6 to about 1.0.

In one embodiment, the catalyst used in the methanol synthesis processincludes an oxide of at least one element selected from the groupconsisting of copper, silver, zinc, boron, magnesium, aluminum,vanadium, chromium, manganese, gallium, palladium, osmium and zirconium.Preferably, the catalyst is a copper based catalyst, more preferably inthe form of copper oxide.

In another embodiment, the catalyst used in the methanol synthesisprocess is a copper based catalyst, which includes an oxide of at leastone element selected from the group consisting of silver, zinc, boron,magnesium, aluminum, vanadium, chromium, manganese, gallium, palladium,osmium and zirconium. Preferably, the catalyst contains copper oxide andan oxide of at least one element selected from the group consisting ofzinc, magnesium, aluminum, chromium, and zirconium. In one embodiment,the methanol synthesis catalyst is selected from the group consistingof: copper oxides, zinc oxides and aluminum oxides. More preferably, thecatalyst contains oxides of copper and zinc.

In yet another embodiment, the methanol synthesis catalyst comprisescopper oxide, zinc oxide, and at least one other oxide. Preferably, theat least one other oxide is selected from the group consisting ofzirconium oxide, chromium oxide, vanadium oxide, magnesium oxide,aluminum oxide, titanium oxide, hafnium oxide, molybdenum oxide,tungsten oxide, and manganese oxide.

In various embodiments, the methanol synthesis catalyst comprises fromabout 10 wt % to about 70 wt % copper oxide, based on total weight ofthe catalyst. Preferably, the methanol synthesis contains from about 15wt % to about 68 wt % copper oxide, and more preferably from about 20 wt% to about 65 wt % copper oxide, based on total weight of the catalyst.

In one embodiment, the methanol synthesis catalyst comprises from about3 wt % to about 30 wt % zinc oxide, based on total weight of thecatalyst. Preferably, the methanol synthesis catalyst comprises fromabout 4 wt % to about 27 wt % zinc oxide, more preferably from about 5wt % to about 24 wt % zinc oxide.

In embodiments in which copper oxide and zinc oxide are both present inthe methanol synthesis catalyst, the ratio of copper oxide to zinc oxidecan vary over a wide range. Preferably in such embodiments, the methanolsynthesis catalyst comprises copper oxide and zinc oxide in a Cu:Znatomic ratio of from about 0.5:1 to about 20:1, preferably from about0.7:1 to about 15:1, more preferably from about 0.8:1 to about 5:1.

The methanol synthesis catalyst is made according to conventionalprocesses. Examples of such processes can be found in U.S. Pat. Nos.6,114,279; 6,054,497; 5,767,039; 5,045,520; 5,254,520; 5,610,202;4,666,945; 4,455,394; 4,565,803; 5,385,949, with the descriptions ofeach being fully incorporated herein by reference.

In one embodiment, the syngas formed in the syngas conversion plant iscooled prior to being sent to the methanol synthesis reactor.Preferably, the syngas is cooled so as to condense at least a portion ofthe water vapor formed during the syngas process.

The methanol synthesis process implemented in the present invention canbe any conventional methanol synthesis process. Examples of suchprocesses include batch processes and continuous processes. Continuousprocesses are preferred. Tubular bed processes and fluidized bedprocesses are particularly preferred types of continuous processes.

In general, the methanol synthesis process takes place according to thefollowing reactions:CO+2H₂→CH₃OH  (5)CO₂+3H₂→CH₃OH+H₂O  (6)

The methanol synthesis process is effective over a wide range oftemperatures. In one embodiment, the syngas is contacted with themethanol synthesis catalyst at a temperature in the range of from about302° F. (150° C.) to about 842° F. (450° C.), preferably in a range offrom about 347° F. (175° C.) to about 662° F. (350° C.), more preferablyin a range of from about 392° F. (200° C.) to about 572° F. (300° C.).

The process is also operable over a wide range of pressures. In oneembodiment, the syngas is contacted with the methanol synthesis catalystat a pressure in the range of from about 15 atmospheres to about 125atmospheres, preferably in a range of from about 20 atmospheres to about100 atmospheres, more preferably in a range of from about 25 atmospheresto about 75 atmospheres.

Gas hourly space velocities vary depending upon the type of continuousprocess that is used. Desirably, gas hourly space velocity of flow ofgas through the catalyst bed is in the range of from about 50 hr-1 toabout 50,000 hr-1. Preferably, gas hourly space velocity of flow of gasthrough the catalyst bed is in the range of from about 250 hr-1 to about25,000 hr-1, more preferably from about 500 hr-1 to about 10,000 hr-1.

The methanol synthesis process produces a variety of hydrocarbons asby-products. According to the methanol composition of this invention, itis desirable to operate the process so as to maximize not only theamount of methanol formed, but also aldehydes and other alcohols whichare particularly desirable in the conversion of oxygenates to olefins.In is particularly appropriate to maximize the amount of methanol formedin the methanol synthesis, and remove hydrocarbons less desirable in theconversion of oxygenates to olefins from the crude methanol productstream formed in the methanol synthesis reactor.

6. Refining Crude Methanol to Make Methanol Product

In conventional methanol synthesis systems, the crude methanol productmixture formed in the methanol synthesis unit is further processed afterreaction to obtain a desirable methanol-containing composition.Processing is accomplished by any conventional means. Examples of suchmeans include distillation, selective condensation, and selectiveadsorption. Process conditions, e.g., temperatures and pressures, canvary according to the particular methanol composition desired. It isparticularly desirable to minimize the amount of water and light boilingpoint components in the methanol-containing composition, but withoutsubstantially reducing the amount of methanol and desirable aldehydesand/or other desirable alcohols also present.

In one processing system, the crude methanol product from the methanolsynthesis reactor is sent to a let down vessel so as to reduce thepressure to about atmospheric or slightly higher. This let down inpressure allows undesirable light boiling point components to be removedfrom the methanol composition as a vapor. The vapor is desirably ofsufficient quality to use a fuel.

In another processing system, the crude methanol is sent from themethanol synthesizing unit to a distillation system. The distillationsystem contains one or more distillation columns which are used toseparate the desired methanol composition from water and hydrocarbonby-products. Desirably, the methanol composition that is separated fromthe crude methanol comprises a majority of the methanol and a majorityof aldehyde and/or alcohol supplements contained in the crude alcoholprior to separation. Preferably, the methanol composition that isseparated from the crude methanol comprises a majority of theacetaldehyde and/or ethanol, if any, contained in the crude methanolprior to separation.

The distillation system optionally includes a step of treating themethanol steam being distilled so as to remove or neutralize acids inthe stream. Preferably, a base is added in the system that is effectivein neutralizing organic acids that are found in the methanol stream.Conventional base compounds can be used. Examples of base compoundsinclude alkali metal hydroxide or carbonate compounds, and amine orammonium hydroxide compounds. In one particular embodiment, about 20 ppmto about 120 ppm w/w of a base composition, calculated asstoichiometrically equivalent NaOH, is added, preferably about 25 ppm toabout 100 ppm w/w of a base composition, calculated asstoichiometrically equivalent NaOH, is added.

The invention can include any distillation system that produces a “fuseloil” stream, which includes C1–C4 alcohols, aldehydes, ketones, estersand water. The fusel oil stream has a boiling point higher than that ofmethanol. It is especially advantageous when the fusel oil stream isliquid taken from a column fed with the crude methanol from the let-downvessel or with the bottoms liquid from a column fed with such crudemethanol, the off-take point being at a level below the feed level.Alternatively or additionally, the fusel oil stream is taken from alevel above the feed level in such a column. Because some of the higheralcohols are advantageous in the methanol composition of this invention,it is desirable to operate the distillation system to recover the C₂–C₄alcohols along with the methanol rather than in the fusel oil stream.

Examples of distillation systems include the use of single and twocolumn distillation columns. Preferably, the single columns operate toremove volatiles in the overhead, methanol product at a high level,fusel oil as vapor above the feed and/or as liquid below the feed, andwater as a bottoms stream.

In one embodiment of a two column system, the first column is a “toppingcolumn” from which volatiles or “light ends” are taken overhead andmethanol liquid as bottoms. A non-limiting list of possible light endsincludes hydrogen, carbon monoxide and methane. The second is a“refining column” from which methanol product is taken as an overheadstream or at a high level, and water is removed as a bottoms stream. Inthis embodiment, the refining column includes at least one off-take forfusel oil as vapor above the feed and/or as liquid below the feed.

In another embodiment of a two column system, the first column is awater-extractive column in which there is a water feed introduced at alevel above the crude methanol feed level. It is desirable to feedsufficient water to produce a bottoms liquid containing over 40% w/wwater, preferably 40% to 60% w/w water, and more preferably 80% to 95%w/w water. This column optionally includes one or more direct fusel oilside off-takes.

In yet another embodiment, the distillation system is one in which anaqueous, semi-crude methanol is taken as liquid above the feed in asingle or refining column. The semi-crude methanol is passed to arefining column, from which methanol product is taken overhead or at ahigh level. Preferably, water or aqueous methanol is taken as a bottomsstream.

Alternatively, undesirable by-products are removed from the crudemethanol stream from the methanol synthesis reactor by adsorption. Insuch a system, fusel oil can be recovered by regenerating the adsorbent.

An exemplary methanol synthesis system is illustrated in FIG. 1 and willnow be described in greater detail. As shown in FIG. 1, a feed stream95, which preferably includes natural gas, is directed to adesulfurization unit 97. Prior to entering the desulfurization unit 97,the feed stream 95 optionally is compressed by one or more compressors,not shown, to facilitate movement of the feed stream 95 and variousintermediate streams through the methanol synthesis system. In oneembodiment, the natural gas from feed stream 95 contacts water fromwater stream 96 in the desulfurization unit 97 in a countercurrentmanner under conditions effective to remove sulfur-containingcomponents, e.g., H₂S and/or mercaptans, therefrom. In this manner, thedesulfurization unit 97 acts as an absorption unit. Additionally oralternatively, the desulfurization unit 97 may act as an adsorptionunit. In this embodiment, the desulfurization unit 97 preferablyincludes one or more columns that are packed with molecular sieveparticles, e.g., 3–5 angstrom molecular sieve particles, the pores ofwhich are adapted to selectively capture the sulfur-containingcomponents from natural gas stream 95. The optional adsorption unitoptionally includes a regeneration system, not shown, for regeneratingdeactivated or partially deactivated molecular sieve particles. If thedesulfurization unit 97 includes an adsorption unit, the feed stream 95preferably is heated to a temperature of between 700° F. (371° C.) and800° F. (427° C.) by a heat exchanger, not shown, before it is directedto desulfurization unit 97. The desulfurization unit 97 formsdesulfurized feed stream 100, which is directed to a reforming unit 101.Preferably, desulfurized feed stream 100 comprises less than 5 weightpercent, more preferably less than 1 weight percent, and most preferablyless than 0.01 weight percent sulfur-containing compounds, based on thetotal weight of the desulfurized feed stream 100.

The reforming unit 101 converts the natural gas in desulfurized feedstream 100 to syngas in syngas stream 98. Generally, the production ofsyngas involves a combustion reaction of natural gas, mostly methane,and an oxygen source, e.g., air, into hydrogen, carbon monoxide and/orcarbon dioxide. Syngas production processes are well known, and includeconventional steam reforming, autothermal reforming, or a combinationthereof. Thus, reforming unit 101 may be a steam reforming unit, apartial oxidation unit, an autothermal reforming unit, and/or a combinedreforming unit, e.g., a unit that combines two or more of thesereforming processes. In one embodiment, water from water stream 96preferably increases the water content of, and more preferablysaturates, the feed stream 95, in the process of removingsulfur-containing components. Additionally or alternatively, thedesulfurized feed stream 100 is directed to a separate saturizationunit, not shown, in which water contacts the desulfurized feed stream100 under conditions effective to saturate the desulfurized feed stream100 or increase the water content thereof. For example, the saturizationunit may include a packed or tray column wherein water contacts thedesulfurized feed stream 100 in a countercurrent manner under conditionseffective to saturate or increase the water content of the desulfurizedfeed stream 100. Saturation of the feed stream 95 and/or desulfurizedfeed stream 100 is particularly beneficial if the reforming unit 101implements a steam reforming process as a water-containing or saturateddesulfurized feed stream 100 may be necessary in order for the steamreforming process to convert the desulfurized feed stream 100 to syngasin syngas stream 98. Additionally or alternatively, water may beinjected directly into the reforming unit 101, particularly if thereforming unit 101 provides a steam reforming process. Resulting syngasstream 98 is directed to a compression zone 99, wherein the syngasstream 98 is compressed in one or more stages to form compressed stream102. Preferably, the compression zone 99 includes one or morecentrifugal compressors. Compressed stream 102 is then directed to amethanol synthesis unit 105, wherein the syngas in compressed stream 102contacts a methanol synthesis catalyst under conditions effective toconvert at least a portion of the syngas to crude methanol in crudemethanol stream 107. Optionally, unreacted syngas from methanolsynthesis unit 105 is recycled to compression zone 99 as shown byunreacted syngas stream 92.

The crude methanol in crude methanol stream 107 includes light ends,methanol, water, and fusel oil. Preferably, prior to introduction intoseparation zone 94, the crude methanol stream 107 is treated with acaustic medium, not shown, in a caustic wash unit, not shown, underconditions effective to increase the pH of the crude methanol stream107. As a result, the crude methanol stream 107 also optionally includesdissolved caustic salts. As shown, crude methanol stream 107 is directedto a separation zone 94, which is adapted to separate one or more ofthese components and isolate a relatively pure methanol stream. Theseparation zone 94 includes a light ends separation unit 110, such as atopping column, and a refining column 113. Crude methanol stream 107 isfirst directed to the light ends separation unit 110, wherein conditionsare effective to separate the crude methanol stream 107 into light endsstream 111 and bottoms crude methanol stream 112, which containsmethanol, water, fusel oil, and optionally dissolved caustic salts. Thelight ends separation unit 110 typically includes from about 50 to about80 trays and has a cross-sectional diameter of from about 8 feet (2.4 m)to about 20 feet (6 m). At least a portion of the light ends stream 111preferably is recycled to methanol synthesis unit 105, as shown, forfurther conversion to methanol while the bottoms crude methanol stream112 is directed to refining column 113 for further processing. Inrefining column 113, the bottoms crude methanol stream 112 is subjectedto conditions effective to separate the bottoms crude methanol stream112 into a refined methanol stream 114, a fusel oil stream 93, and awater stream 115. A majority of the caustic salts, if any, from bottomscrude methanol stream 112 are dissolved in water stream 115. Preferably,refined methanol stream 114 contains at least 95.0 weight percent, morepreferably at least 99.0 weight percent and most preferably at least99.5 weight percent methanol, based on the total weight of the refinedmethanol stream 114. Preferably, refined methanol stream 114 containsless than 0.25 weight percent, more preferably less than 1 weightpercent and most preferably less than 5 weight percent water, based onthe total weight of the refined methanol stream 114. The refining column113 typically includes from about 80 to about 120 trays and has across-sectional diameter of from about 10 feet (3.0 m) to about 24 feet(7.2 m).

C. Ethanol Synthesis Systems

As indicated above, the present invention, in one embodiment, providesfor a combined process for forming methanol and ethanol and convertingthe methanol and ethanol to light olefins in an OTO reaction system. Anon-limiting description of several ethanol synthesis systems that maybe incorporated into the present invention will now be described.

As with methanol synthesis, there are numerous technologies availablefor producing ethanol. The preferred embodiment for forming ethanolaccording to the present invention comprises the reaction of methanol,carbon monoxide, and optionally hydrogen in the presence of a catalystcomposition to form ethanol and water. This reaction is typicallyreferred to as a homologation reaction, and may be illustrated asfollows:CH₃OH+CO+2H₂→CH₃CH₂OH+H₂O  (7)

According to the present invention, the homologation reaction optionallyis catalyzed using a group VII transition metal compound as catalyst anda halogen as the promoter. Many other metal compounds and promoters,however, can be used. Optionally, secondary activators or ligands may beused in conjunction with the metal catalysts and promoters. Thesesecondary activators can be other metallic salts or compounds, amines,phosphorus compounds, as well as a multitude of other compounds thathave been disclosed in the published literature. Thus, a typicalcatalyst system for the homologation of methanol to ethanol comprises ametal atom-containing catalyst, a promoter and optionally ligands,solvents and/or secondary activators.

A variety of references disclose the homologation of methanol toethanol. For example, U.S. Pat. No. 4,133,966 to Pretzer et al., theentirety of which is incorporated herein by reference, discloses aprocess for the homologation of methanol to ethanol using a catalystsystem containing cobalt, acetylacetonate, a trivalent phosphorus ortrivalent arsenic or trivalent antimony organic ligand, an iodinecompound and a ruthenium compound. U.S. Pat. No. 4,111,837 to Taylor,the entirety of which is incorporated herein by reference, relates tothe use of a heterogeneous co-catalyst system for the homologation ofalkanols. The co-catalyst system contains cobalt, and rhenium metal. InU.S. Pat. No. 4,233,466 and U.S. Pat. No. 4,253,987, the entireties ofwhich are both incorporated herein by reference, both to Fiato, thereare disclosed processes and catalysts for the production of ethanol bythe homologation reaction of methanol and syngas using a systemcontaining cobalt atoms, rhenium atoms, iodine atoms and a phosphineligand. U.S. Pat. Nos. 4,239,924 and 4,239,925, both to Pretzer et al.,the entireties of which are also incorporated herein by reference,disclose a process for selectively processing ethanol using a systemcontaining a specifically defined cobalt tricarbonyl complex, an iodinecompound, and a rhenium compound in the methanol homologation reaction.Specifically, the '924 patent discloses the use of aliphatic substitutedcomplexes, while the '925 patent discloses aromatric substitutedcomplexes. U.S. Pat. No. 4,324,927 to Gauthier-Lafaye, the entirety ofwhich is incorporated herein by reference, describes a process for thehomologation of methanol to produce ethanol using a system containingcobalt atoms, rhenium atoms, and both an alkyl halide and an ionichalide. U.S. Pat. No. 4,304,946 to Isogai, the entirety of which isincorporated herein by reference, describes the homologation of methanolto produce ethanol using a cobalt sulfide compound or a mixture of acobalt sulfide compound and a nitrogen-containing and/or aphosphorus-containing compound. This system is free of iodine atoms.U.S. Pat. No. 4,328,379 to Devon, the entirety of which is incorporatedherein by reference, describes the homologation of methanol to produceethanol using a cobalt-iodine catalyst system in the presence of aperfluorocarboxylate anion. U.K. Patent Application GB 2,083,465A toIsogai, the entirety of which is incorporated herein by reference,discloses the homologation of methanol to produce ethanol using aheterogeneous catalyst system comprising cobalt phosphate as the maincatalyst. The applicants also disclose the use of a Group VIII metal asco-catalyst. U.S. Pat. No. 4,954,665 to the Vidal, the entirety of whichis incorporated herein by reference, is directed to a process forproducing ethanol at high efficiency, selectivity and conversion rate.The process comprises a homologation reaction of methanol and carbonmonoxide and hydrogen using a catalyst system containing an alkali metalatom, a cobalt atom, an iodine atom, and, optionally, a ruthenium atomas well as an organic tertiary amino compound. Other U.S. patents thatdescribe producing ethanol (and/or higher alcohols) from methanol, e.g.,via methanol homologation, include U.S. Pat. No. 4,954,665; U.S. Pat.No. 4,608,447; U.S. Pat. No. 4,825,013; U.S. Pat. No. 4,533,775; U.S.Pat. No. 4,540,836; U.S. Pat. No. 4,578,375; U.S. Pat. No. 4,476,326;U.S. Pat. No. 4,424,384; U.S. Pat. No. 4,451,678; U.S. Pat. No.4,409,404; U.S. Pat. No. 4,346,020; U.S. Pat. No. 4,423,258; U.S. Pat.No. 4,423,257, U.S. Pat. No. 4,361,499; U.S. Pat. No. 4,370,507; andU.S. Pat. No. 4,352,946, the entireties of which are all incorporatedherein by reference.

The homologation reaction may occur at a variety of reaction conditions.In one embodiment, the homologation reaction temperature in thehomologation zone ranges from about 650° F. (343° C.) to about 300° F.(149° C.), preferably from about 600° F. (316° C.) to about 400° F.(204° C.), and most preferably from about 550° F. (288° C.)to about 450°F. (232° C.). The pressure in the homologation zone also may varywidely, although the pressure preferably is in the range of the pressureof the syngas that is directed to the methanol synthesis unit, discussedabove. Optionally, the pressure in the homologation zone ranges fromabout 900 psia (6206 kpaa) to about 4,000 psia (27,580 kpaa), preferablyfrom about 1,000 psia (6,895 kPaa) to about 2,000 psia (13,790 kPaa),and most preferably from about 1,200 psia (8,274 kpaa) to about 1,500psia (10,343 kPaa).

Although many different homologation catalysts may be utilized in thehomologation zone to facilitate conversion of the methanol containedtherein to ethanol, the homologation catalyst preferably is selectedfrom the group consisting of potassium oxides, cobalt-molybdenumsulfides, nickel-molybdenum sulfides and potassium carbonates.

Many soluble halides may be used as a promoter in the catalyst systemalthough it is preferred that iodine or its derivatives, e.g., iodineions, be so employed. Illustrative sources of iodide ions includeelemental iodine; cobalt iodide; hydrogen iodide; the alkyl iodideshaving from 1 to 10 carbon atoms such as methyl iodide, ethyl iodide,propyl iodide, 2-ethyhexyl iodide, n-decyl iodide, and the like. Anyother source of iodide that will ionize to form free iodide ions in thereaction medium can be used as the promoter. One can also employ any ofthe organic iodine compounds that will furnish iodide to the reactionmedium. Further, one can use mixtures of iodine and/or iodide compounds,if so desired. The preferred source of the iodide is elemental iodine.

The concentration of acidic iodine atoms in the homologation reactoroptionally is from about 0.000013 to about 1.6 moles per liter;preferably from about 0.026 to about 0.6 mole per liter.

The alkali metal atom component of the catalyst system can come from anyof the known ionic compounds of the alkali metals sodium, potassium,lithium, rubidium and cesium. Preferred alkali metal atom components arederived from sodium salts and potassium salts. Illustrative sourcesthereof include sodium iodide, sodium bicarbonate, sodium carbonate,sodium nitrate, sodium nitrite, sodium sulfate, sodium bisulfate, sodiumchromate, sodium permanganate, sodium chlorate, sodium persulfate,sodium tetraborate, sodium bromide, sodium chloride, sodium fluoride,sodium sulfite, sodium hypochlorite, as well as any other ionic salt ofsodium. Rather than repeat the individual compound names, thecorresponding potassium, lithium, rubidium and cesium salts areillustrative of useful ionic compounds.

The concentration of alkali metal atoms in the homologation reactoroptionally is from about 0.00013 to about 1 mole per liter; preferablyfrom about 0.07 to about 0.6 mole per liter.

As indicated, an organic tertiary amino compound of the general formulaR₃N optionally is present as a co-promoter in the system. The use ofsuch additives is known, as are their identities, to those skilled inthis art. In this formula R represents an organic moiety. The additivecan serve as a catalyst stabilizer and/or to further enhance efficiency,conversion rate and selectivity, especially when the reaction is carriedout at higher temperature. The additive also serves to inhibit equipmentcorrosion in some instances. However, the use of the additive is notmandatory and the reaction can be carried out without it.

A large number of organic amines is known to those skilled in the art asuseful and any of these can be used provided they do not have an adverseeffect on the reaction. Among those of particular utility are thetertiary amines such as trimethylamine, triethylamine, tri-n-butylamine,tri-t-butylamine, tri-2-ethylhexylamine, methyl dibutylamine,tridodecylamine, tristearylamine, ethyl dibutylamine,tricyclohexylamine, triphenylamine, tri(4-methoxyphenyl)amine,tri(p-chlorophenyl)-amine, dibutyl phenylamine, dipentylcyclopentylamine, ethyl diphenylamine, trinaphthylaminetri-p-tolylamine, tri-benzylamine, tri(3-methylcyclohexyl)amine, as wellas other tertiary amines. These organic amines and many others are knownin the art. They can be used singly or, if one desires, in mixturescontaining two or more ligands.

The concentration of the R₃N ligand in the homologation reactoroptionally varies from about 0.000013 to about 0.08 mole per liter;preferably from about 0.02 to about 0.04 mole per liter.

Preferably, hydrogen and carbon monoxide are present in the syngas thatis directed to the homologation reactor. The molar ratio of H₂:CO in thesyngas that is directed to the homologation zone can vary from about20:1 to about 1:20, from about 10:1 to about 1:10, and preferably fromabout 3:1 to about 1:3. Particularly in continuous operations, but alsoin batch experiments, the carbon monoxide-hydrogen gaseous mixture mayalso be used in conjunction with up to 50% by volume of one or moreother gases. These other gases may include one or more inert gases suchas nitrogen, argon, neon and the like, or they may include gases thatmay, or may not, undergo reaction under CO hydrogenation conditions,such as carbon dioxide, hydrocarbons such as methane, ethane, propaneand the like, ethers such as dimethyl ether, methylethyl ether anddiethyl ether, alkanols such as methanol and acid esters such as methylacetate.

Higher alcohols and carboxylic acid esters may also be formed whilecarrying out the process of this invention. Most often these derivativesare n-propanol, methyl formate, methyl acetate, ethyl acetate, ethylether, etc. The major by-products of the process such as the highermolecular weight alcohols and carboxylic acid esters, are, of course,also useful compounds and major articles of commerce. The higheralcohols, the carboxylic acid esters and ethers can easily be separatedfrom one another by conventional means, e.g., fractional distillation invacuo, if desired.

The novel process of this invention can be conducted in a batch,semi-continuous or continuous fashion. The catalyst may be initiallyintroduced into the homologation zone batchwise, or it may becontinuously or intermittently introduced into such a zone during thecourse of the synthesis reaction. Operating conditions can be adjustedto optimize the formation of the ethanol product, and after recovery ofthe alcohol and other products, a fraction rich in the catalystcomposition may then be recycled to the reaction zone, if desired, andadditional products generated. Preferably, the homologation zone is in afixed bed reactor.

As is known in this art, one can additionally have an inert solventpresent in the reaction mixture. A wide variety of substantially inertsolvents are useful in the process of this invention includinghydrocarbon and oxygenated hydrocarbon solvents. Suitable oxygenatedhydrocarbon solvents are compounds comprising carbon, hydrogen andoxygen and those in which the only oxygen atoms present are in ethergroups, ester groups, ketone carbonyl groups or hydroxyl groups ofalcohols. Generally, the oxygenated hydrocarbon will contain 3 to 12carbon atoms and preferably a maximum of 3. oxygen atoms. The solventpreferably is substantially inert under reaction conditions, isrelatively non-polar and has a normal boiling point of at least 65° C.at atmospheric pressure, and preferably, the solvent will have a boilingpoint greater than that of ethanol and other oxygen-containing reactionproducts so that recovery of the solvent by distillation is facilitated.

Preferred ester type solvents are the aliphatic and acylic carboxylicacid monoesters as exemplified by butyl acetate, methyl benzoate,isopropyl iso-butyrate, and propyl propionate as well as dimethyladipate. Useful alcohol-type solvents include monohydric alcohols suchas cyclohexanol, 1-hexanol, 2-hexanol, neopentanol, 2-octanol, etc.Suitable ketone-type solvents include, for example, cyclic ketones suchas cyclohexanone, 2-methylcyclohexanone, as well as acylic ketones suchas 2-pentanone, butanone, acetophenone, etc. Ethers that may be utilizedas solvents include cyclic, acyclic and heterocyclic materials.Preferred ethers are the heterocyclic ethers as illustrated by1,4-dioxane and 1,3-dioxane. Other suitable ether solvents includeisopropyl propyl ether, diethylene glycol dibutyl ether, dibutyl ether,ethyl butyl ether, diphenyl ether, heptyl phenyl ether, anisole,tetrahydrofuran, etc. The most useful solvents of all of the abovegroups include the ethers as represented by monocyclic, heterocyclicethers such a 1,4-dioxane or p-dioxane, etc. Hydrocarbon solvents, suchas hexane, heptane, decane, dodecane, tetradecane, etc. are alsosuitable solvents for use in this invention. In the practice of thisinvention, it is also possible to add a small amount of water to thesolvent and still obtain satisfactory results.

The reaction time varies depending upon the reaction parameters, reactorsize and charge, and the individual components employed at the specificprocess conditions.

D. OTO Reaction Systems

The present invention, in one embodiment, provides for combining amethanol synthesis system with a homologation unit and an OTO reactionsystem, which is discussed in more detail hereinafter. As used herein,“reaction system” means a system comprising a reaction zone, optionallya disengaging zone, optionally a catalyst regenerator, optionally acatalyst cooler and optionally a catalyst stripper.

Typically, molecular sieve catalysts have been used to convert oxygenatecompounds to light olefins. Ideally, the molecular sieve catalystcomposition comprises an alumina or a silica-alumina catalystcomposition. Silicoaluminophosphate (SAPO) molecular sieve catalysts areparticularly desirable in such conversion processes, because they arehighly selective in the formation of ethylene and propylene. Anon-limiting list of preferable SAPO molecular sieve catalystcompositions includes SAPO-17, SAPO-18, SAPO-34, SAPO-35, SAPO-44, thesubstituted forms thereof, and mixtures thereof. Preferably, themolecular sieve catalyst composition comprises a molecular sieveselected from the group consisting of: SAPO-5, SAPO-8, SAPO-11, SAPO-16,SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37,SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47, SAPO-56, AEI/CHAintergrowths, metal containing forms thereof, intergrown forms thereof,and mixtures thereof.

Although the present application is specifically directed to combining amethanol/ethanol synthesis system with an OTO reaction system, one ormore additional components may be included in the feedstock that isdirected to the OTO reaction system. For example, the feedstock that isdirected to the OTO reaction system optionally contains, in addition tomethanol and ethanol, one or more aliphatic-containing compounds such asalcohols, amines, carbonyl compounds for example aldehydes, ketones andcarboxylic acids, ethers, halides, mercaptans, sulfides, and the like,and mixtures thereof. The aliphatic moiety of the aliphatic-containingcompounds typically contains from 1 to about 50 carbon atoms, preferablyfrom 1 to 20 carbon atoms, more preferably from 1 to 10 carbon atoms,and more preferably from 1 to 4 carbon atoms, and most preferablymethanol.

Non-limiting examples of aliphatic-containing compounds include:alcohols such as methanol and ethanol, alkyl-mercaptans such as methylmercaptan and ethyl mercaptan, alkyl-sulfides such as methyl sulfide,alkyl-amines such as methyl amine, alkyl-ethers such as DME, diethylether and methylethyl ether, alkyl-halides such as methyl chloride andethyl chloride, alkyl ketones such as dimethyl ketone, alkyl-aldehydessuch as formaldehyde and acetaldehyde, and various acids such as aceticacid.

In a preferred embodiment of the process of the invention, the feedstockcontains one or more oxygenates in addition to methanol and ethanol or,more specifically, one or more organic compounds containing at least oneoxygen atom. In the most preferred embodiment of the process ofinvention, the oxygenate in the feedstock (in addition to methanol andethanol) comprises one or more alcohols, preferably aliphatic alcoholswhere the aliphatic moiety of the alcohol(s) has from 1 to 20 carbonatoms, preferably from 1 to 10 carbon atoms, and most preferably from 1to 4 carbon atoms. The alcohols useful as feedstock in the process ofthe invention include lower straight and branched chain aliphaticalcohols and their unsaturated counterparts. Non-limiting examples ofoxygenates, in addition to methanol and ethanol, include n-propanol,isopropanol, methyl ethyl ether, DME, diethyl ether, di-isopropyl ether,formaldehyde, dimethyl carbonate, dimethyl ketone, acetic acid, andmixtures thereof. In the most preferred embodiment, the feedstockcomprises methanol, ethanol and one or more of DME, diethyl ether or acombination thereof.

The various feedstocks discussed above are converted primarily into oneor more olefins. The olefins or olefin monomers produced from thefeedstock typically have from 2 to 30 carbon atoms, preferably 2 to 8carbon atoms, more preferably 2 to 6 carbon atoms, still more preferably2 to 4 carbons atoms, and most preferably ethylene and/or propylene.

Non-limiting examples of olefin monomer(s) include ethylene, propylene,butene-1, pentene-1,4-methyl-pentene-1, hexene-1, octene-1 and decene-1,preferably ethylene, propylene, butene-1, pentene-1,4-methyl-pentene-1,hexene-1, octene-1 and isomers thereof. Other olefin monomers includeunsaturated monomers, diolefins having 4 to 18 carbon atoms, conjugatedor nonconjugated dienes, polyenes, vinyl monomers and cyclic olefins.

In a preferred embodiment, the feedstock, which contains methanol andethanol, is converted in the presence of a molecular sieve catalystcomposition into olefin(s) having 2 to 6 carbons atoms, preferably 2 to4 carbon atoms. Most preferably, the olefin(s), alone or combination,are converted from a feedstock containing an oxygenate, preferably analcohol, most preferably methanol, to the preferred olefin(s) ethyleneand/or propylene.

The most preferred process is generally referred to as an oxygenate toolefins (OTO) reaction process. In an OTO process, typically anoxygenated feedstock, most preferably a methanol- and ethanol-containingfeedstock, is converted in the presence of a molecular sieve catalystcomposition into one or more olefins, preferably and predominantly,ethylene and/or propylene, referred to herein as light olefins.

The feedstock, in one embodiment, contains one or more diluents,typically used to reduce the concentration of the feedstock. Thediluents are generally non-reactive to the feedstock or molecular sievecatalyst composition. Non-limiting examples of diluents include helium,argon, nitrogen, carbon monoxide, carbon dioxide, water, essentiallynon-reactive paraffins (especially alkanes such as methane, ethane, andpropane), essentially non-reactive aromatic compounds, and mixturesthereof. The most preferred diluents are water and nitrogen, with waterbeing particularly preferred. In other embodiments, the feedstock doesnot contain any diluent.

The diluent may be used either in a liquid or a vapor form, or acombination thereof. The diluent is either added directly to a feedstockentering into a reactor or added directly into a reactor, or added witha molecular sieve catalyst composition. In one embodiment, the amount ofdiluent in the feedstock is in the range of from about 1 to about 99mole percent based on the total number of moles of the feedstock anddiluent, preferably from about 1 to 80 mole percent, more preferablyfrom about 5 to about 50, most preferably from about 5 to about 25. Inone embodiment, other hydrocarbons are added to a feedstock eitherdirectly or indirectly, and include olefin(s), paraffin(s), aromatic(s)(see for example U.S. Pat. No. 4,677,242, addition of aromatics) ormixtures thereof, preferably propylene, butylene, pentylene, and otherhydrocarbons having 4 or more carbon atoms, or mixtures thereof.

The process for converting a feedstock, especially a feedstockcontaining one or more oxygenates, in the presence of a molecular sievecatalyst composition of the invention, is carried out in a reactionprocess in a reactor, where the process is a fixed bed process, afluidized bed process (includes a turbulent bed process), preferably acontinuous fluidized bed process, and most preferably a continuous highvelocity fluidized bed process.

The reaction processes can take place in a variety of catalytic reactorssuch as hybrid reactors that have a dense bed or fixed bed reactionzones and/or fast fluidized bed reaction zones coupled together,circulating fluidized bed reactors, riser reactors, and the like.Suitable conventional reactor types are described in for example U.S.Pat. No. 4,076,796, U.S. Pat. No. 6,287,522 (dual riser), andFluidization Engineering, D. Kunii and O. Levenspiel, Robert E. KriegerPublishing Company, New York, N.Y. 1977, which are all herein fullyincorporated by reference.

The preferred reactor type are riser reactors generally described inRiser Reactor, Fluidization and Fluid-Particle Systems, pages 48 to 59,F. A. Zenz and D. F. Othmer, Reinhold Publishing Corporation, New York,1960, and U.S. Pat. No. 6,166,282 (fast-fluidized bed reactor), and U.S.patent application Ser. No. 09/564,613 filed May 4, 2000 (multiple riserreactor), which are all herein fully incorporated by reference.

In an embodiment, the amount of liquid feedstock fed separately orjointly with a vapor feedstock, to a reactor system is in the range offrom 0.1 weight percent to about 85 weight percent, preferably fromabout 1 weight percent to about 75 weight percent, more preferably fromabout 5 weight percent to about 65 weight percent based on the totalweight of the feedstock including any diluent contained therein. Theliquid and vapor feedstocks are preferably the same composition, orcontain varying proportions of the same or different feedstock with thesame or different diluent.

The conversion temperature employed in the conversion process,specifically within the reactor system, is in the range of from about392° F. (200° C.) to about 1832° F. (1000° C.), preferably from about482° F. (250° C.) to about 1472° F. (800° C.), more preferably fromabout 482° F. (250° C.) to about 1382° F. (750° C.), yet more preferablyfrom about 572° F. (300° C.) to about 1202° F. (650° C.), yet even morepreferably from about 662° F. (350° C.) to about 1112° F. (600° C.) mostpreferably from about 662° F. (350° C.) to about 1022° F. (550° C.).

The conversion pressure employed in the conversion process, specificallywithin the reactor system, varies over a wide range including autogenouspressure. The conversion pressure is based on the partial pressure ofthe feedstock exclusive of any diluent therein. Typically the conversionpressure employed in the process is in the range of from about 0.1 kPaato about 5 MPaa, preferably from about 5 kPaa to about 1 MPaa, and mostpreferably from about 20 kPaa to about 500 kPaa.

The weight hourly space velocity (WHSV), particularly in a process forconverting a feedstock containing one or more oxygenates in the presenceof a molecular sieve catalyst composition within a reaction zone, isdefined as the total weight of the feedstock excluding any diluents tothe reaction zone per hour per weight of molecular sieve in themolecular sieve catalyst composition in the reaction zone. The WHSV ismaintained at a level sufficient to keep the catalyst composition in afluidized state within a reactor.

Typically, the WHSV ranges from about 1 hr-1 to about 5000 hr-1,preferably from about 2 hr-1 to about 3000 hr-1, more preferably fromabout 5 hr-1 to about 1500 hr-1, and most preferably from about 10 hr-1to about 1000 hr-1. In one preferred embodiment, the WHSV is greaterthan 20 hr-1, preferably the WHSV for conversion of a feedstockcontaining methanol, DME, or both, is in the range of from about 20 hr-1to about 300 hr-1.

The superficial gas velocity (SGV) of the feedstock including diluentand reaction products within the reactor system is preferably sufficientto fluidize the molecular sieve catalyst composition within a reactionzone in the reactor. The SGV in the process, particularly within thereactor system, more particularly within the riser reactor(s), is atleast 0.1 meter per second (m/sec), preferably greater than 0.5 m/sec,more preferably greater than 1 m/sec, even more preferably greater than2 m/sec, yet even more preferably greater than 3 m/sec, and mostpreferably greater than 4 m/sec. See for example U.S. patent applicationSer. No. 09/708,753 filed Nov. 8, 2000, which is herein incorporated byreference.

E. Integrated Reaction System

As indicated above, in one embodiment, the present invention is directedto a process for forming an alcohol-containing stream, which comprisesmethanol and ethanol. The methanol is synthesized in a methanolsynthesis unit, and the ethanol is synthesized in an ethanol synthesisunit, which preferably includes a homologation zone. Thealcohol-containing stream is particularly suitable for use in an OTOreaction system. Thus, in one embodiment, the present invention isdirected to a system for producing light olefins, which system comprisesa methanol synthesis unit, an ethanol synthesis unit and an OTO reactionsystem.

In another embodiment, the invention is to a process for producing lightolefins. The process includes a step of contacting syngas in thepresence of one or more metal-containing catalyst to produce a firstfeedstock comprising methanol. A portion of the methanol is converted ina homologation zone to a second feedstock comprising ethanol. The secondfeedstock optionally also includes methanol. The first feedstock and thesecond feedstock are introduced to a process for converting the methanoland the ethanol in the present of a molecular sieve catalyst compositionto light olefins.

Ideally, the first and second feedstocks are combined to form a combinedfeedstock before being introduced to the process for converting themethanol and the ethanol to light olefins. In this embodiment, thecombined feedstock optionally comprises methanol, ethanol and water. Aweight majority of the water preferably is removed from the combinedfeedstock before being introduced to the process for converting themethanol and the ethanol to light olefins.

The combined feedstock also may include light ends such as carbonmonoxide, methane and hydrogen. If so, then the process preferablyincludes a step of removing the light ends from at least a portion ofthe combined feedstock.

As indicated above, the combined feedstock includes both methanol andethanol. Ideally, the combined feedstock has a methanol to ethanolweight ratio of from about 4.0:1.0 to about 99.0:1.0, more preferablyfrom about 9.0:1.0 to about 19.0:1.0.

In one embodiment of the present invention, the process of convertingthe methanol and the ethanol in the presence of a molecular sievecatalyst composition to the light olefins also produces carbon monoxide.In this embodiment, the carbon monoxide optionally is separated from thelight olefins. The separated carbon monoxide then may be directed to thehomologation zone to provide a carbon monoxide source for the step ofconverting a portion of the methanol to the second feedstock.

Similarly, in one embodiment of the present invention, the process ofconverting the methanol and the ethanol in the presence of a molecularsieve catalyst composition to the light olefins also produces hydrogen.In this embodiment, the hydrogen optionally is separated from the lightolefins. The separated hydrogen then may be directed to the homologationzone to provide a hydrogen source for the step of converting a portionof the methanol to the second feedstock.

In another embodiment, the invention is to an integrated process forproducing light olefins. In this aspect of the invention, syngascontacts one or more metal-containing catalysts to produce a firstfeedstock comprising methanol. A portion of the methanol preferablycontacts carbon monoxide in the presence of a catalyst system to producea second feedstock comprising ethanol. The first feedstock and thesecond feedstock, optionally in a combined stream, are introduced to aprocess for converting the methanol and the ethanol in the presence of amolecular sieve catalyst composition to the light olefins.

In another embodiment, the invention is directed to a process forproducing light olefins, which includes a step of contacting a syngasstream with a methanol synthesis catalyst under first conditionseffective to form a methanol-containing stream comprising methanol. Atleast a portion of the methanol-containing stream contacts carbonmonoxide and a homologation catalyst under second conditions effectiveto form a mixed alcohol stream comprising methanol and ethanol. At leasta portion of the mixed alcohol stream contacts a molecular sievecatalyst composition under third conditions effective to convert themethanol and the ethanol to the light olefins.

Optionally, the mixed alcohol stream further comprises water and theprocess further comprises the step of separating a weight majority ofthe water from the mixed alcohol stream. The second conditionsoptionally comprise a holomogation reaction temperature of from about204° C. to about 316° C. Optionally, the process further comprises astep of separating the mixed alcohol stream into a first fraction and asecond fraction. The first fraction comprises a weight majority of themethanol present in the mixed alcohol stream, and the second fractioncomprises a weight majority of the ethanol present in the mixed alcoholstream.

Another embodiment of the present invention is directed to a process forproducing alcohols. In this embodiment, the invention includes a step ofcontacting a first syngas stream comprising carbon monoxide and hydrogenwith a methanol synthesis catalyst in a methanol synthesis zone underfirst conditions effective to form a methanol-containing streamcomprising hydrogen, carbon monoxide, methanol and water. A secondsyngas stream comprising carbon monoxide and optionally hydrogencontacts a methanol-containing feed stream and a homologation catalystin a homologation zone under second conditions effective to form anethanol-containing stream comprising carbon monoxide, methanol, ethanol,water and optionally hydrogen. At least a portion of themethanol-containing stream is combined with at least a portion of theethanol-containing stream to form a combined stream. At least a portionof the combined stream is separated in a light ends removal unit into afirst fraction and a second fraction. The first fraction comprises aweight majority of the hydrogen and carbon monoxide present in the atleast a portion of the combined stream. The second fraction comprises aweight majority of the methanol, ethanol, and water present in the atleast a portion of the combined stream. Water is removed from at least aportion of the second fraction in a water removal unit to form a thirdfraction and a fourth fraction. The third fraction comprises a weightmajority of the methanol and ethanol present in the at least a portionof the second fraction. The fourth fraction comprises a weight majorityof the water present in the at least a portion of the second fraction.The third fraction is separated into the methanol-containing feed streamand a final product stream, wherein the final product stream comprisesmethanol and ethanol.

Optionally, the methanol-containing feed stream and the final productstream are aliquot portions of the third fraction, and themethanol-containing feed stream comprises methanol and ethanol.Optionally, this inventive process further comprises a step ofcontacting at least a portion of the final product stream with amolecular sieve catalyst composition under third conditions effective toconvert the methanol and ethanol to light olefins. Optionally, theprocess further includes a step of separating the final mixed alcoholstream into a fifth fraction and a sixth fraction. The fifth fractioncomprises a weight majority of the methanol present in the final mixedalcohol stream, and the sixth fraction comprises a weight majority ofthe ethanol present in the final mixed alcohol stream. Optionally, atleast a portion of the fifth fraction contacts a molecular sievecatalyst composition under third conditions effective to convert themethanol contained therein into light olefins. Additionally oralternatively, at least a portion of the sixth fraction contacts amolecular sieve catalyst composition under third conditions effective toconvert the ethanol contained therein to light olefins. Preferably, thestep of contacting at a least a portion of the sixth fraction with amolecular sieve catalyst composition occurs in a fixed bed reactionsystem.

In another embodiment, the invention is directed to a process forproducing light olefins. This process comprises a step of contacting asyngas stream comprising carbon monoxide, hydrogen and optionally carbondioxide with a methanol synthesis catalyst under first conditionseffective to form a methanol-containing stream comprising methanol andwater. At least a portion of the methanol-containing stream contactscarbon monoxide, optionally hydrogen and a homologation catalyst undersecond conditions effective to form a mixed alcohol stream comprisingmethanol, ethanol, and water. At least a portion of the mixed alcoholstream contacts a molecular sieve catalyst composition in a reactionsystem under third conditions effective to convert the methanol andethanol to light olefins. An effluent stream is yielded from thereaction system and comprises an ethylene to propylene weight ratio fromabout 0.9:1.0 to about 2.2:1.0, preferably from about 1.1:1.0 to about1.4:1.0.

In one embodiment, the invention comprises a step of contacting a firstsyngas stream comprising carbon monoxide, hydrogen and optionally carbondioxide with a methanol synthesis catalyst in a methanol synthesis zoneunder first conditions effective to form a methanol-containing streamcomprising hydrogen, carbon monoxide, methanol and water. A secondsyngas stream comprising carbon monoxide and optionally hydrogencontacts a methanol-containing feed stream and a homologation catalystin a homologation zone under second conditions effective to form anethanol-containing stream comprising carbon monoxide, methanol, ethanol,water and optionally hydrogen. At least a portion of themethanol-containing stream is combined with at least a portion of theethanol-containing stream to form a combined stream. At least a portionof the carbon monoxide, water and hydrogen are removed from at least aportion of the combined stream to form a final mixed alcohol stream. Afirst portion of the final mixed alcohol stream is directed to thehomologation zone to serve as the methanol-containing feed stream. Asecond portion of the final mixed alcohol stream contacts a molecularsieve catalyst composition in a reaction system under third conditionseffective to conver the methanol and ethanol to light olefins. Aneffluent stream, which has an ethylene to propylene weight ratio of fromabout 0.9:1.0 to about 2.2:1.0, preferably from about 1.1:1.0 to about1.4:1.0, is yielded from the reaction system.

In this embodiment, the first portion of the final mixed alcohol streamand the second portion of the final mixed alcohol stream optionally arealiquot portions of the final mixed alcohol stream. Themethanol-containing feed stream optionally comprises methanol andethanol. Optionally, this inventive process further comprises a step ofseparating the final mixed alcohol stream into a first fraction and asecond fraction. The first fraction comprises a weight majority of themethanol present in the final mixed alcohol stream, and the secondfraction comprises a weight majority of the ethanol present in the finalmixed alcohol stream. In this embodiment, the first portion of the finalmixed alcohol stream optionally comprises a first portion of the firstfraction. Optionally, the reaction system comprises a fast-fluidizedreaction zone and a fixed bed reaction zone. A second portion of thefirst fraction is directed to the fast fluidized reaction zone forconversion of the methanol contained therein to light olefins. At leasta portion of the second fraction is directed to the fixed bed reactionsystem for the conversion of the ethanol contained therein to lightolefins.

Optionally, the homologation zone is made part of an existing methanolsynthesis system. In this embodiment, the beds in the methanol synthesisunit preferably are replaced with beds suitable for the homologationreaction. Additionally or alternatively, a second ethanol synthesis unithaving a homologation zone can be incorporated into a methanol synthesissystem, as described below with reference to FIGS. 2–4.

FIGS. 2–4 of the present specification illustrate three non-limitingexamples of integrated systems according to three embodiments of thepresent invention.

FIG. 2 illustrates one embodiment of the present invention wherein themethanol synthesis unit operates in parallel to the ethanol synthesisunit. As shown, a natural gas stream 200 comprising natural gas isdirected to a syngas generation unit 201. Ideally, the natural gasstream 200 comprises less than 5 weight percent, more preferably lessthan 1 weight percent, and most preferably less than 0.01 weight percentsulfur-containing compounds, based on the total weight of the naturalgas stream 200. In the syngas generation unit 201, the natural gas innatural gas stream 200 contacts oxygen under conditions effective toconvert the natural gas into syngas, which is yielded from the syngasgeneration unit 201 in syngas stream 202. Generally, the production ofsyngas involves a combustion reaction of natural gas, mostly methane andan oxygen source, e.g., air, into hydrogen carbon monoxide and/or carbondioxide. Syngas production process are well known, and includeconventional steam reforming, autothermal reforming, or a combinationthereof. Thus, syngas generation unit 201 may be a steam reforming unit,a partial oxidation unit, an autothermal reforming unit, and/or acombined reforming unit, e.g., a unit that combines two or more of thesereforming processes. Optionally, water from a water stream, not shown,is added to the natural gas stream 200 or the syngas generation unit 201in order to increase the water content of, and preferably saturate, thenatural gas stream 200. Natural gas stream 200 optionally isdesulfurized and/or saturated by any of the methods described above withreference to FIG. 1.

Syngas stream 202 ideally is compressed in one or more compressors, notshown, and is divided into a first derivative syngas stream 204 and asecond derivative syngas stream 203. Optionally, the syngas in firstderivative syngas stream 204 is compressed to provide idealpressurization characteristics for methanol synthesis. Similarly, secondderivative syngas stream 203 optionally is compressed to provide idealpressurization characteristics for conversion thereof to ethanol inethanol synthesis unit 206. First derivative syngas stream 204, or aportion thereof, is directed to a methanol synthesis unit 205 whereinthe syngas in first derivative syngas stream 204 contacts a methanolsynthesis catalyst under conditions effective to convert the syngas tomethanol. Thus, methanol synthesis unit 205 yields a methanol-containingstream 207, which optionally comprises light ends, methanol, water, andfusel oil. Optionally, prior to the separation of the componentscontained in methanol-containing stream 207, the methanol-containingstream 207 is treated with a caustic medium, not shown, in a causticwash unit, not shown, under conditions effective to increase the pH ofthe methanol-containing stream 207.

Meanwhile, second derivative syngas stream 203, or a portion thereof, isdirected to ethanol synthesis unit 206, wherein the syngas in the secondderivative syngas stream 203 contacts methanol and a homologationcatalyst composition under conditions effective to form ethanol, whichis yielded from the ethanol synthesis unit 206 in ethanol-containingstream 208. Additionally, ethanol-containing stream 208 optionallycomprises methanol, light ends, water, 208 optionally is treated in acaustic wash unit, not shown, to increase the pH thereof. As shown inFIG. 2, the methanol-containing stream 207 is combined with theethanol-containing stream 208 to form combined alcohol-containing stream209.

Combined alcohol-containing stream 209 preferably is directed to aseparation zone, which comprises a light ends separation unit 210, suchas a topping column, and a refining column 213. In the light endsseparation unit 210, conditions are effective to separate the combinedalcohol-containing stream 209 into light ends stream 211 and bottomsalcohol stream 212.

At least a portion of light ends stream 211 preferably is recycled toone or more of the syngas generation unit 201, the methanol synthesisunit 205, and/or the ethanol synthesis unit 206. As shown, stream 224,the flow of which is regulated by flow control device 233, carries lightends from light ends stream 211 to one or more of these units.Specifically, stream 227 carries the light ends from stream 224 to thesyngas generation unit 201. Similarly, stream 225 carries light endsfrom stream 224 to the ethanol synthesis unit 206. Likewise, stream 226carries light ends from stream 224 to the methanol synthesis unit 205.The flow of the light ends through these various streams optionally iscontrolled via flow control devices 229, 232 and 231. As shown, aportion of the components in stream 224 can be removed from the systemvia purge stream 228. The flow rate at which components are removed fromthe system via purge stream 228 optionally is controlled via flowcontrol device 230.

In one embodiment, the light ends separation unit 210 also functions asa caustic wash unit. As shown, a caustic stream 235 is introduced to thelight ends separation unit 210 under conditions effective to increasethe pH of the combined alcohol-containing stream 209 after it has beenintroduced therein. Thus, bottoms alcohol stream 212 may include causticsalts from caustic stream 235.

As shown, bottoms alcohol stream 212 is directed to refining column 213,wherein water and optionally fusel oil, not shown, are separated fromthe methanol and ethanol contained in bottoms alcohol stream 212. Thus,bottoms alcohol stream 212 is separated into a water-containing stream215, a fusel oil stream, not shown, and a refined alcohol stream 214,which preferably, in this embodiment, is directed to a methanolconcentrator 216. Water-containing stream 215 preferably contains aweight majority of the caustic salts that were contained in bottomsalcohol stream 212.

In methanol concentrator 216, refined alcohol stream 214 preferably issubjected to conditions effective to form methanol concentrated stream217 and methanol diluted stream 218. Methanol concentrated stream 217comprises a weight majority of the methanol contained in refined alcoholstream 214 and optionally a portion of the ethanol contained in refinedalcohol stream 214. Conversely, methanol diluted stream 218 comprises aweight majority of the ethanol contained in refined alcohol stream 214and optionally a portion of the methanol contained in refined alcoholstream 214. The purpose of the methanol concentrator is to form a streamconcentrated in methanol (the methanol concentrated stream 217), aportion of which may be directed to the ethanol synthesis unit 206 toserve as a methanol source for the homologation reaction. As shown,methanol concentrated stream 217 is separated, preferably in aliquotportions, into recycle stream 219 and stream 220. Recycle stream 219preferably is rich in methanol and is directed to ethanol synthesis unit206 to serve as a methanol source for the homologation reactionoccurring therein. The flow of the recycle stream 219 optionally iscontrolled via flow control device 234.

Stream 220, which is derived from methanol concentrated stream 217,preferably is combined with at least a portion of the methanol dilutedstream 218 to form combined alcohol stream 221.

Combined alcohol stream 221, which comprises largely methanol andethanol, is then directed to an OTO reactor 222 wherein the methanol andethanol contained in the combined alcohol stream 221 contact one or moremolecular sieve catalyst compositions under conditions effective to formethylene and propylene, which are yielded from the OTO reactor 222 inlight olefins containing stream 223.

In another embodiment, not shown, stream 220 is not combined withmethanol diluted stream 218. Instead, stream 220 is directed to an MTOreactor, not shown, wherein the methanol contained in stream 220contacts one more molecular sieve catalyst compositions under conditionseffective to convert the methanol contained therein to ethylene andpropylene. In this embodiment, methanol diluted stream 218 optionally isdirected to an ethanol to olefins (ETO) reactor, not shown, wherein theethanol contained in methanol diluted stream 218 contacts one or moremolecular sieve catalyst compositions under conditions effective toconvert the ethanol contained therein to ethylene. In this embodiment,the reactor type and/or reaction conditions of the MTO and ETO reactorsmay differ from one another in order to provide optimized conditions forconverting the methanol to light olefins in the MTO reactor and forconverting the ethanol to ethylene in the ETO reactor.

FIG. 3 illustrates another embodiment of the present invention whereinthe methanol synthesis unit and the ethanol synthesis unit are situatedin series rather than in parallel. As shown, natural gas stream 300comprising natural gas is directed to a syngas generation unit 301wherein the natural gas is converted to syngas in syngas stream 302.Syngas generation unit 301 optionally comprises a steam reforming unit,a partial oxidation unit, an autothermal reforming unit, and/or acombined reforming unit, e.g., a unit that combines two or more of thesereforming processes. As above, natural gas stream 300 optionally issaturated with water prior to or upon introduction into syngasgeneration unit 301. Syngas stream 302 preferably is directed to acompression zone, not shown, wherein the syngas stream 302 is compressedto a pressure favorable for conversion thereof to methanol. Aftercompression, syngas stream 302 is directed to methanol synthesis unit305 for conversion thereof to methanol. In the methanol synthesis unit,the syngas stream 302 contacts one or more methanol synthesis catalystsunder conditions effective to convert at least a portion of the syngasto crude methanol, which is yielded from the methanol synthesis unit viamethanol-containing stream 307. Optionally, unreacted syngas frommethanol synthesis unit 305 is recycled to the compression zone.

Methanol-containing stream 307, which is yielded from the methanolsynthesis unit 305, preferably comprises light ends, methanol, water andfusel oil. As shown, at least a portion of methanol-containing stream307 is directed to an ethanol synthesis unit 306, which preferablycomprises a homologation zone. In the ethanol synthesis unit 306, atleast a portion of the methanol-containing stream 307 contacts carbonmonoxide, preferably hydrogen, and optionally carbon dioxide in thepresence of one or more homologation catalysts under conditionseffective to form ethanol. The ethanol formed in ethanol synthesis unit306 is yielded therefrom via ethanol-containing stream 308.

Depending on reaction conditions and the specific catalyst used in theethanol synthesis unit 306, all or a portion of the methanol that wasintroduced into the ethanol synthesis unit 306 may be converted toethanol. As it is desirable according to the present invention toprovide an alcohol-containing stream that comprises both methanol andethanol, a portion of the methanol from methanol-containing stream 307optionally bypasses the ethanol synthesis unit 306, as shown by bypassstream 337, the flow of which is controlled by flow control device 336.Ideally, as shown in FIG. 3, bypass stream 337 is recombined withethanol-containing stream 308 prior to the introduction thereof into theseparation zone for removal of undesirable components therefrom.

As shown, ethanol-containing stream 308, which comprises methanol,ethanol, water, light ends, and fusel oil is introduced into light endsseparation unit 310. In light ends separation unit 310, the light endsin ethanol-containing stream 308 are separated from the other componentscontained therein. Specifically, in light ends separation unit 310, theethanol-containing stream 308 is subjected to conditions effective toform light ends stream 311 and bottoms alcohol stream 312. Light endsstream 311 preferably comprises a weight majority of the light ends thatwere contained in ethanol-containing stream 308, while the bottomsalcohol stream 312 comprises a weight majority of the methanol, ethanol,water and fusel oil present in the ethanol-containing stream 308.

Preferably, a portion of light ends stream 311 is directed throughstream 324 to one or more of the syngas generation unit 301, themethanol synthesis unit 305, and/or the ethanol synthesis unit 306. Asillustrated, stream 324 is directed to the syngas generation unit 301via stream 327, to the methanol synthesis unit 305 via stream 326, andto the ethanol synthesis unit 306 via stream 325. The flow rate at whichthe light ends stream 311, or a portion thereof, is directed to theseunits may be varied by flow control devices 329, 331, 332, and/or 333.Preferably, a portion of the light ends are purged from the system viapurge stream 328, the flow of which may be controlled by flow controldevice 330.

As indicated above, light ends separation unit 310 optionally alsofunctions as a caustic wash unit. As shown, caustic stream 335 isintroduced into light ends separation unit 310 under conditionseffective to increase the pH of the bottoms alcohol stream 312. As aresult, bottoms alcohol stream 312 optionally comprises caustic salts inaddition to methanol, ethanol, water and fusel oil. As shown, bottomsalcohol stream 312 is directed to a refining column 313 for removal ofthe water contained therein. Thus, refining column 313 operates toseparate the bottoms alcohol stream 312 into a refined alcohol stream314 and a water-containing stream 315. Preferably, water-containingstream 315 comprises a weight majority of the water that was present inthe bottoms alcohol stream 312. Similarly, refined alcohol stream 314preferably comprises a weight majority of the methanol and ethanolcontained in bottoms alcohol stream 312. Refining column 313 optionallyalso forms a side draw stream, not shown, whereby a weight majority ofthe fusel oil that was contained in bottoms alcohol stream 312 isremoved therefrom. Refined alcohol stream 314, which comprises methanoland ethanol, may then be directed to an OTO reactor 322, wherein themethanol and ethanol contained therein are converted to light olefins,which are yielded from the OTO reactor 322 via light olefins containingstream 323.

FIG. 4 illustrates another embodiment of the present invention whereinmethanol synthesis and ethanol synthesis occur in a single reactionzone. As shown, natural gas stream 400 comprising natural gas isdirected to a syngas generation unit 401, which optionally comprises asteam reforming unit, a partial oxidation unit, an autothermal reformingunit, and/or a combined reforming unit. As with the above embodiments,water is optionally added to natural gas stream 400 and/or syngasgeneration unit 401 in order to increase the water content thereof. Insyngas generation unit 401, the natural gas from natural gas stream 400is converted to syngas, which is yielded from the syngas generation unit401 via syngas stream 402.

Syngas stream 402 preferably is directed to a combined synthesis unit406 wherein, at least initially, the syngas from syngas stream 402contacts one or more catalyst compositions under conditions effective toform methanol and water, which are yielded from the combined synthesisunit 406 via alcohol stream 408. Combined synthesis unit 406 preferablyalso receives methanol from a methanol source. The methanol that isreceived in combined synthesis unit 406 preferably contacts carbonmonoxide and preferably hydrogen as well as one or more homologationcatalysts under conditions effective to form ethanol. Thus, combinedsynthesis unit 406 contains both a methanol synthesis catalyst and ahomologation catalyst and operates to form both methanol and ethanol,which are yielded from the combined synthesis unit with water, lightends, and fusel oil via alcohol stream 408.

Alcohol stream 408 preferably is then directed to a separation zone. Asshown, alcohol stream 408 is directed to a light ends separation unit410, wherein the alcohol stream 408 is separated into a light endsstream 411 and a bottoms alcohol stream 412. Light ends stream 411preferably comprises a weight majority of the light ends that werepresent in alcohol stream 408, while bottoms alcohol stream 412preferably comprises a weight majority of the methanol, ethanol, fuseloil and water that was present in alcohol stream 408. Ideally, at leasta portion of light ends stream 411 is recycled to one or more of thesyngas generation unit 401 and/or the combined synthesis unit 406. Asshown, stream 427 and stream 426 delivere the light ends to the syngasgeneration unit and the combined synthesis unit, respectively. The flowrate at which the light ends are delivered to these units optionally iscontrolled via flow control devices 429, 431 and 433. If recycle of thelight ends is desired, then a portion of light ends stream 411preferably is purged from the reaction system, as shown by purge stream428. The flow rate at which undesirable components are removed from thereaction system optionally is controlled by flow control device 430.

As indicated above, light ends separation unit 410 optionally alsofunctions as a caustic wash unit in order to increase the pH of thestreams yielded therefrom. As shown, caustic stream 435 is introducedinto light ends separation unit 410. As a result, bottoms alcohol stream412 optionally comprises caustic salts in addition to methanol, ethanol,water and fusel oil.

Bottoms alcohol stream 412 is then directed to a refining column 413wherein water and fusel oil are separated from the methanol and ethanolcontained in bottoms alcohol stream 412. Specifically, upon introductioninto refining column 413, bottoms alcohol stream 412 is subjected toconditions effective to form a refined alcohol stream 414 and awater-containing stream 415. Preferably water-containing stream 415comprises a weight majority of the water contained in bottoms alcoholstream 412. Similarly, refined alcohol stream 414 preferably comprises aweight majority of the methanol and ethanol contained in bottoms alcoholstream 412. Additionally, a weight majority of the fusel oil containedin bottoms alcohol stream preferably is yielded from the refining column413 via a side draw stream, not shown. In this embodiment, in order toprovide a methanol source for the combined synthesis unit 406, all or aportion of refined alcohol stream 414 preferably is directed to amethanol concentrator 416. Upon introduction into methanol concentrator416, the refined alcohol stream 414 is subjected to conditions effectiveto form methanol concentrated stream 417 and methanol diluted stream418. Methanol concentrated stream 417 preferably comprises a weightmajority of the methanol that was contained in the refined alcoholstream 414, while the methanol diluted stream 418 preferably comprises aweight majority of the ethanol contained in the refined alcohol stream414.

A portion of methanol concentrated stream 417 preferably is thendirected to the combined synthesis unit 406 as shown by recycle stream419. The flow rate at which methanol is supplied to the combinedsynthesis unit 406 optionally is controlled by flow control device 434.The remaining portion of methanol concentrated stream 417, illustratedby stream 420, preferably is combined with methanol diluted stream 418to form a combined alcohol stream 421. Combined alcohol stream 421 isthen directed to an OTO reactor 422, wherein the methanol and ethanolcontained in the combined alcohol stream 421 contact one or moremolecular sieve catalyst compositions under conditions effective to formethylene and propylene, which are yielded therefrom in lightolefin-containing stream 423.

The reaction conditions in the combined synthesis unit 406 may varywidely. In one embodiment, the conditions include a pressure of about1400 psig (9653 kPag), and a temperature ranging from 400° F. to 500° F.(204° C. to 260° C.). The feed gas composition that is directed to thecombined synthesis unit 406 optionally comprises about 85 molar percenthydrogen, about 3 molar percent carbon monoxide, about 2 molar percentcarbon dioxide and about 10 molar percent methane. At these conditions,homologation catalysts such as K₂CO₂/CoMo Sulfides will convert thesynthesized methanol into ethanol. It has been found that even at highH₂/CO ratios, the amount of hydrocarbons (fully saturated,non-oxygenated) formed in the combined synthesis unit 406 at theseconditions is acceptably low (about 2 weight percent at 550° F. (288°C.)).

In another embodiment, not shown, stream 420 is not combined withmethanol diluted stream 418 prior to conversion thereof to lightolefins. Instead, as discussed above with reference to FIG. 2, stream420 is directed to an MTO reactor wherein the methanol contained instream 420 contacts one or more molecular sieve catalyst compositionsunder conditions effective to convert the methanol contained therein tolight olefins. Similarly, the ethanol contained in methanol dilutedstream 418 can be directed to an ETO reactor wherein the ethanolcontained therein contacts one or more molecular sieve catalystcompositions under conditions effective to convert the ethanol containedin the methanol diluted stream 418 to ethylene. In this manner, thereactor type and reaction conditions of the MTO reactor and the ETOreactor may differ in order to provide optimized reaction conditions forconverting the methanol in stream 420 to light olefins and the ethanolin methanol diluted stream 418 to ethylene.

F. Controlling the Ratio of Ethylene to Propylene Formed in an OTOReaction System

It has been discovered that ethanol has a selectivity for ethylene underOTO and ETO reaction conditions, which approaches 100 weight percent.Methanol, in contrast, produces ethylene and propylene in generallyequal amounts under OTO and ETO reaction conditions. By increasing theamount of ethanol contained in an OTO feedstock, the amount of ethyleneproduced in the OTO reaction system relative to propylene can beadvantageously increased.

In one aspect of the invention, the ratio of ethylene to propyleneformed in an OTO reaction system can be controlled by varying the ratioof the methanol to ethanol that is sent to the OTO reaction system. Asindicated above, methanol converts to ethylene and propylene inrelatively equal amounts in an OTO reaction system, while ethanolconverts almost entirely to ethylene. As a result, as the amount ofethanol contained in an OTO feedstock is increased relative to methanol,the amount of ethylene produced in the OTO reaction system willincrease. Thus, the amount of ethylene relative to propylene formed inan OTO reaction system advantageously can be controlled by controllingthe ratio of methanol to ethanol contained in the OTO feedstock.

The weight ratio of methanol to ethanol contained in an OTO feedstockcan be controlled by a variety of ways. For example, if the integratedsystem comprises a methanol synthesis unit that is separate from theethanol synthesis unit, then one or more flow control devices may beused to control the flow of methanol from the methanol synthesis unitand the amount of ethanol from the ethanol synthesis unit that isdirected to the OTO reaction system. Additionally or alternatively, theamount and/or type of catalyst in the ethanol synthesis unit and/or themethanol synthesis unit can be varied to control ratio of the alcoholsformed therein. If the integrated system includes a single combinedsynthesis unit, which forms both the methanol and methanol, then theweight ratio of the methanol synthesis catalyst to the ethanol synthesiscatalyst (e.g., homologation catalyst) contained in the combinedsynthesis unit can be controlled to provide a desired methanol toethanol weight ratio.

Additionally or alternatively, the reaction conditions in the ethanolsynthesis unit, e.g., temperature, can be varied to control ratio of theethanol formed therein. Generally, an increase in reaction temperaturein an ethanol synthesis unit, within reason, increases the amount ofethanol formed in the ethanol synthesis unit.

Thus, in one aspect of the invention, the ratio of ethylene to propyleneformed in an OTO reaction system can be controlled by varying thereaction temperature in an ethanol synthesis unit, which, in cooperationwith a methanol synthesis unit, produces the feedstock for the OTOreaction system. That is, an increase in the reaction temperature of anethanol synthesis unit will increase the amount of ethanol formed,which, ultimately, will increase the amount of ethylene that is formedin the OTO reaction system. In this manner, the amount of ethylenerelative to propylene formed in an OTO reaction system advantageouslycan be controlled by controlling the reaction temperature of the ethanolsynthesis unit.

Table I, below, illustrates the relationship of temperature and ethanolproduction in one prophetic ethanol synthesis system. In thehomologation zone of the ethanol synthesis system, the pressure was heldat approximately 1400 psig (9653 kPag) and the gas hourly space velocitywas held constant at approximately 2500 hr⁻¹. The catalyst implementedin the ethanol synthesis system was comprised of K₂CO₃/sulfided CoMohomologation catalyst. The feed to the homologation zone was comprisedof methanol, CO, and H₂ in molar fractions of 0.128, 0.436, and 0.436,respectively. The ethanol synthesis system operated in parallel to amethanol synthesis unit, as described above with reference to FIG. 2.

TABLE I Ethanol Production as a Function of Temperature ReactionTemperature Weight Percent Ethanol ° F. (° C.) in OTO Feedstock 450(232) 5.7 500 (260) 7.7 550 (288) 9.8

The data in Table I clearly confirms that as temperature is increased ina homologation zone, the amount of ethanol formed therein increases.

G. EXAMPLES

The present invention will be better understood in view of the followingnon-limiting examples.

Example I (Control) Methanol as OTO Feedstock

In Example I, which is a control example, a feedstock comprising 99.5weight percent methanol (˜0.5 weight percent water) was directed to anOTO microflow reactor for conversion thereof to light olefins. Theresulting effluent stream was then analyzed to determine the amount ofethylene relative to propylene formed in the microflow reactor. Theamounts of other products formed in the microflow reactor were alsodetermined.

A SAPO-34 molecular sieve catalyst composition, designated catalystcomposition “A”, was formulated following U.S. Pat. No. 6,440,894, theentirety of which is incorporated herein by reference. The silicon toaluminum atomic ratio of the as-synthesized SAPO-34 molecular sieve usedto form the catalyst composition was determined to be 0.068 based onInductively Coupled Plasma (ICP) spectroscopy analysis. The formulatedcatalyst composition had the following overall composition: 40 weightpercent molecular sieve, 12 weight percent ACH (aluminum chlorhydrol)binder and with the rest (48 weight percent) being kaolin clay matrixmaterial, based on the total weight of the formulated catalystcomposition. For each run, 95 mg of the molecular sieve catalystcomposition was mixed with 1 g of 100-μm silicon-carbide. The resultingmixture was loaded into the microflow reactor, which was made of 0.25inch silicon-steel tubing. The reactor temperature was increased to thedesired reaction temperature (475° C. for control Example I) while thecatalyst was under He flow (46 ml/min), and was held at that temperaturefor about 30 to 40 minutes for temperature stabilization.

The oxygenate-containing feed was introduced into the reactor at 80μl/min, 100 WHSV and 25 psig (175 kPag) while the effluent was sampledby a 16-loop Valco valve. The reactor effluent formed was sampled in amulti-loop sampling valve to obtain the gas phase selectivity data. Fromabout 9 to 15 samples were analyzed for each set of conditions to obtainthe weighed average selectivity. After each test run, oxygen/He waspassed through the catalyst to measure the coke deposit.

A mixture of 10 ml/min of O₂ and 10 ml/min of helium was flowed throughthe reactor for catalyst regeneration while the reactor temperature wasincreased from 475° C. to 550° C. A portion of the regeneration gasstream was sent into a nickel-containing methanator, which converted COand CO₂ in the effluent stream into methane in the presence of an excessamount of H₂. The concentration of methane was then quantified by a FIDdetector. The amount of coke on the removed sieve was then measured bycomparing the integrated peak area from the FID detector with that of acalibration standard.

The collected effluent samples were analyzed by on-line gaschromatography (Hewlett Packard 6890) equipped with a flame ionizationdetector. The chromatographic column used was a Plot Q column.

The weighed averages (selectivities) of the effluent samples werecalculated based on the following formula,(x₁)(y₁)+(x₂−x₁)(y₂)+(x₃−x₂)(y₂+y₃)/2+(x₄−x₃)(y₃+y₄)/2+ . . . , wherex_(i) and y_(i) are yield and g methanol fed/g sieve, respectively.Catalyst Lifetime (g/g catalyst) reported is methanol that wascumulatively converted. Note that both the lifetime and WHSV werereported based on the weight of the sieve. Methanol converted at lessthan about 10 weight percent conversion was not included in thecalculations.

Coke selectivities were calculated based on the FID measurement of theend-of-run coke (EOR) and the catalyst lifetime, i.e., Coke selectivity,weight percent=EOR coke (g coke/g sieve)/{lifetime (g methanol/gsieve)*14/32 (g CH₂/g methanol)}*100.

The selectivity of methanol conversion to the various products weredetermined through gas chromatography. The results are provided in TableII, below. The data provided in each of the columns of Table II (exceptReaction Temperature and Catalyst Lifetime, which is recorded in g/gcatalyst) are weight percentages, based on the total weight of theeffluent produced. C₁, C₂ ⁼, C₂ ⁰, C₃ ⁼, C₃ ⁰, ACAD, C₄+, C₂ ⁼+C₃ ⁼ inthe following Tables refer to methane, ethylene, ethane, propylene,propane, acetaldehyde, hydrocarbons containing four or more carbonatoms, and ethylene and propylene combined, respectively.

TABLE II Selectivity and Conversion of Feedstock Comprising 100 Wt.Percent Methanol to Light Olefins Reaction Catalyst Temp. C₁ C₂ ^(═) C₂⁰ C₃ ^(═) C₃ ⁰ ACAD C₄+ Coke C₂ ^(═) + C₃ ^(═) C₂ ^(═)/C₃ ^(═) Lifetime475° C. 1.61 35.94 0.28 39.20 0.61 — 22.34 2.28 75.13 0.92 20.50

As indicated in Table II, above, the prime olefin selectivity (POS) forthe conversion of a pure methanol feedstock at 475° C., 25 psig and 100WHSV was 75.13 weight percent. The ratio of ethylene to propylene formedwas 0.92.

Example II 9:1 Methanol to Ethanol Wt. Ratio in OTO Feedstock

In Example II, a feedstock comprising 90 weight percent methanol and 10weight percent ethanol was directed to an OTO microflow reactor forconversion thereof to light olefins. The oxygenate-containing feed wasintroduced into the reactor containing Catalyst Composition A under thesame conditions as indicated above for Example I (100 WHSV and 25 psig(175 kPag)). Unlike Example I, however, 9 to 15 runs were performed foreach of the following reaction temperatures: 425° C., 450° C., 475° C.and 500° C. to determine what effect, if any, temperature had onconversion and selectivity of a mixed alcohol-containing feedstock tolight olefins.

The resulting effluent stream was then analyzed in the manner describedabove in Example I to determine the amount of ethylene relative topropylene that was formed in the OTO reactor. The amounts of otherproducts formed in the microflow reactor were also determined. Theresults of the analysis are indicated below in Table III.

TABLE III Selectivity and Conversion of Feedstock Comprising 90 Wt.Percent Methanol and 10 Wt. Percent Ethanol to Light Olefins ReactionCatalyst Temp. C₁ C₂ ^(═) C₂ ⁰ C₃ ^(═) C₃ ⁰ ACAD C₄+ Coke C₂ ^(═) + C₃^(═) C₂ ^(═)/C₃ ^(═) Lifetime 425° C. 1.00 35.66 0.21 32.81 0.39 3.2425.26 1.44 68.47 1.09 33.28 450° C. 1.12 39.99 0.22 35.83 0.37 1.3920.06 1.00 75.83 1.12 46.73 475° C. 1.23 43.86 0.30 35.07 0.44 0.9716.78 1.35 78.92 1.25 31.38 500° C. 2.47 47.76 0.45 31.03 0.42 1.6314.11 2.13 78.79 1.54 20.49

As indicated above, the prime olefin selectivity (POS) for theconversion of a feedstock comprising pure 90 weight percent methanol and10 weight percent ethanol ranged from 68.47 to 78.79 depending onreaction temperature. The ratio of ethylene to propylene formed rangedfrom 1.09 to 1.54 also depending on reaction temperature.

The data from this example illustrates a surprising and unexpectedflexibility in the ability to tune the ratio of ethylene to propyleneformed in an OTO reaction system by modifying the reaction temperaturewhen the feedstock comprises a mixture of methanol and ethanol. Forexample, the ethylene to propylene ratio increased from 0.92 to 1.25with the 10 weight percent ethanol/90 weight percent methanol feedstock,which is an increase of 36 percent. Furthermore, the data from thisexample at 475° C. illustrates that the overall POS also improved withthe 10 weight percent ethanol/90 weight percent methanol feedstock whencompared with the pure methanol feed that was conducted under the sameexperimental conditions in Example I. For example, the POS for the mixedfeed was 78.92 weight percent, an increase of 5 percent. Moreimportantly, the ethylene selectivity increased by 22 percent (or 7.92weight percent) with the 10 weight percent ethanol/90 weight percentmethanol feedstock.

Example III 8:2 Methanol to Ethanol Ratio in OTO Feedstock

In Example III, a feedstock comprising 80 weight percent methanol and 20weight percent ethanol was directed to an OTO microflow reactor forconversion thereof to light olefins. The oxygenate-containing feed wasintroduced into the reactor containing Catalyst Composition A under thesame conditions as indicated above for Example I (100 WHSV and 25 psig(175 kPag)). Unlike Example I, however, runs were performed for each ofthe following reaction temperatures: 450° C., 475° C. and 500° C. todetermine what effect, if any, temperature had on conversion andselectivity of a mixed alcohol-containing feedstock to light olefins.

The resulting effluent stream was then analyzed in the manner describedabove in Example I to determine the amount of ethylene relative topropylene that was formed in the OTO reactor. The amounts of otherproducts formed in the microflow reactor were also determined. Theresults of the analysis are indicated below in Table IV.

TABLE IV Selectivity and Conversion of Feedstock Comprising 80 Wt.Percent Methanol and 20 Wt. Percent Ethanol to Light Olefins ReactionCatalyst Temp. C₁ C₂ ^(═) C₂ ⁰ C₃ ^(═) C₃ ⁰ ACAD C₄+ Coke C₂ ^(═) + C₃^(═) C₂ ^(═)/C₃ ^(═) Lifetime 450° C. 0.79 46.01 0.27 30.65 0.38 2.4218.18 1.29 76.67 1.51 37.59 475° C. 0.99 47.98 0.35 30.17 0.43 2.2115.92 1.95 78.15 1.59 22.63 500° C. 2.30 52.57 0.50 24.30 0.30 4.8012.79 2.45 76.87 2.16 26.61

The data from this example also illustrates a surprising and unexpectedflexibility in the ability to tune the ratio of ethylene to propyleneformed in an OTO reaction system by modifying the reaction temperaturewhen the feedstock comprises a mixture of methanol and ethanol. Forexample, the ethylene to propylene ratio increased from 0.92 to 1.59with the 20 weight percent ethanol/80 weight percent methanol feedstock,which is an increase of 73 percent. When the reaction temperature wasraised to 500° C., the ethylene/propylene ratio reached 2.16, asurprising and unexpected breakthrough as far as the economics of theprocess are concerned. The ethylene selectivity at 475° C. increased byabout 34 percent (or 12 weight percent) over control when the feedstockcontained 20 weight percent ethanol and 80 weight percent methanol.

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to variations notnecessarily illustrated herein. For this reason, then, reference shouldbe made solely to the appended claims for purposes of determining thetrue scope of the present invention.

1. A process for producing light olefins, the process comprising thesteps of: (a) contacting syngas in the presence of one or moremetal-containing catalysts to produce a first feedstock comprisingmethanol; (b) converting a portion of the methanol in a homologationzone to a second feedstock comprising ethanol by contacting the portionof the methanol with a homologation catalyst selected from the groupconsisting of potassium oxides, cobalt-molybdenum sulfides,nickel-molybdenum sulfides and potassium carbonates; and (c) introducingthe first feedstock and the second feedstock to a process for convertingthe methanol and the ethanol in the presence of a silicoaluminophosphatemolecular sieve catalyst composition to the light olefins, wherein thecombined feedstock has a methanol to ethanol weight ratio of from4.0:1.0 to 19.0:1.0 and the process for converting the methanol and theethanol to light olefms is carried out at a temperature of from 475° C.to 500° C.
 2. The process of claim 1, wherein the second feedstockfurther comprises methanol.
 3. The process of claim 1, wherein theprocess further comprises the step of: (d) combining the first feedstockand the second feedstock to form a combined feedstock prior toconverting in the presence of the catalyst.
 4. The process of claim 3,wherein the combined feedstock comprises methanol, ethanol and water. 5.The process of claim 4, wherein the process further comprises the stepof: (e) removing a weight majority of the water from the combinedfeedstock prior to converting in the presence of the catalyst.
 6. Theprocess of claim 4, wherein the combined feedstock further compriseslight ends, the process further comprising the step of: (e) removing thelight ends from at least a portion of the combined feedstock, whereinthe light ends comprise carbon monoxide, methane and hydrogen.
 7. Theprocess of claim 1, wherein the molecular sieve catalyst compositioncomprises a molecular sieve selected from the group consisting of:SAPO-5, SAPO-8, SALPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31,SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44,SAPO-47, SAPO-56, AEI/CHA intergrowths, metal containing forms thereof,intergrown forms thereof, and mixtures thereof.
 8. The process of claim1, wherein step (b) further comprises contacting the portion of themethanol with the homologation catalyst in the presence of carbonmonoxide, optionally hydrogen and optionally carbon dioxide.
 9. Theprocess of claim 8, wherein the process for converting the methanol andthe ethanol in the presence of a molecular sieve catalyst composition tothe light olefins also produces carbon monoxide, wherein the carbonmonoxide is separated from the light olefins and is directed to thehomologation zone to provide a carbon monoxide source for step (b). 10.The process of claim 1, wherein the one or more metal-containingcatalysts comprises one or more of copper oxides, zinc oxides andaluminum oxides.
 11. The process of claim 1, wherein the process furthercomprises the step of: (d) contacting a natural gas stream with oxygenunder conditions effective to convert the natural gas stream into thesyngas.
 12. An integrated process for producing light olefins, theprocess comprising the steps of: (a) contacting syngas with one or moremetal-containing catalysts to produce a first feedstock comprisingmethanol; (b) contacting a portion of the methanol with carbon monoxidein the presence of a catalyst system containing a catalyst selected fromthe group consisting of potassium oxides, cobalt-molybdenum sulfides,nickel-molybdenum sulfides and potassium carbonates to produce a secondfeedstock comprising ethanol; and (c) introducing the first feedstockand the second feedstock to a process for converting the methanol andthe ethanol in the presence of a silicoaluminophosphate molecular sievecatalyst composition to the light olefins, wherein the combinedfeedstock has a methanol to ethanol weight ratio of from 4.0:1.0 to19.0:1.0 and the process for convening the methanol and the ethanol tolight olefins is carried our at a temperature of from 475°C. to 500° C.13. The integrated process of claim 12, wherein the second feedstockfurther comprises methanol.
 14. The integrated process of claim 12,wherein the process further comprises the step of: (d) combining thefirst feedstock and the second feedstock to form a combined feedstockprior to converting in the presence of the catalyst.
 15. The integratedprocess of claim 14, wherein the combined feedstock comprises methanol,ethanol and water.
 16. The integrated process of claim 15, wherein theprocess further comprises the step of: (e) removing a weight majority ofthe water from the combined feedstock prior to converting in thepresence of the catalyst.
 17. The integrated process of claim 15,wherein the combined feedstock further comprises light ends, the processfurther comprising the step of: (e) removing the light ends from atleast a portion of the combined feedstock, wherein the light endscomprise carbon monoxide, methane and hydrogen.
 18. The integratedprocess of claim 12, wherein the molecular sieve catalyst compositioncomprises a molecular sieve selected from the group consisting of:SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31,SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44,SAPO-47, SAPO-56, AEI/CHA intergrowths, metal containing forms thereof,intergrown forms thereof, and mixtures thereof.
 19. The integratedprocess of claim 12, wherein the one or more metal-containing catalystscomprises one or more of copper oxides, zinc oxides and aluminum oxides.20. The integrated process of claim 12, wherein the process furthercomprises the step of: (d) contacting a natural gas stream with oxygenunder conditions effective to convert the natural gas stream into thesyngas.
 21. A process for producing light olefins, the processcomprising the steps of: (a) contacting a syngas stream with a methanolsynthesis catalyst under first conditions effective to form amethanol-containing stream comprising methanol; (b) contacting at leasta portion of the methanol-containing stream with carbon monoxide and ahomalogation catalyst selected from the group consisting of potassiumoxides, cobalt-molybdenum sulfides, nickel-molybdenum sulfides andpotassium carbonates and forming a mixed alcohol stream comprisingmethanol and ethanol at a methanol to ethanol weight ratio of from4.0:1.0 to 19.0:1.0; and (c) contacting at least a portion of the mixedalcohol stream with a silicoaluminophosphate molecular sieve catalystcomposition at a temperature of from 475° C. to 500° C. to convert themethanol and the ethanol to the light olefins.
 22. The process of claim21, wherein the mixed alcohol stream further comprises water, theprocess further comprising the step of: (d) separating a weight majorityof the water from the mixed alcohol stream.
 23. The process of claim 21,wherein the molecular sieve catalyst composition comprises a molecularsieve selected from the group consisting of: SAPO-5, SAPO-8, SAPO-11,SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36,SAPO-37, SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47, SAPO-56, AEI/CHAintergrowths, metal containing forms thereof, intergrown forms thereof,and mixtures thereof.
 24. The process of claim 21, wherein the methanolsynthesis catalyst is selected from the group consisting of: copperoxides, zinc oxides and aluminum oxides.
 25. The process of claim 21,wherein the mixed alcohol stream further comprises light ends, theprocess further comprising the step of: d) removing the light ends fromat least a portion of the mixed alcohol stream, wherein the light endscomprise carbon monoxide, methane and hydrogen.
 26. The process of claim21, wherein the process further comprises the step of: d) separating themixed alcohol stream into a first fraction and a second fraction,wherein the first fraction comprises a weight majority of the methanolpresent in the mixed alcohol stream, and wherein the second fractioncomprises a weight majority of the ethanol present in the mixed alcoholstream.
 27. The process of claim 21, wherein the process furthercomprises the step of: (d) contacting a natural gas stream with oxygenunder conditions effective to convert the natural gas stream into thesyngas stream.
 28. A process for producing light olefins, wherein theprocess comprises the steps of: (a) contacting a syngas streamcomprising carbon monoxide, hydrogen and optionally carbon dioxide witha methanol synthesis catalyst under first conditions effective to form amethanol-containing steam comprising methanol and water; (b) contactingat least a portion of the methanol-containing stream with carbonmonoxide and a homologation catalyst selected from the group consistingof potassium oxides, cobalt-molybdenum sulfides, nickel-molybdenumsulfides and potassium carbonates and forming a mixed alcohol streamcomprising methanol and ethanol at a methanol to ethanol weight ratio offrom 4.0:1.0 to 19.0:1.0; (c) contacting at least a portion of the mixedalcohol stream with a silicoaluminophosphate molecular sieve catalystcomposition in a reaction system at a temperature of from 475° C. to500° C. to convert the methanol and ethanol to light olefins; (d)yielding an effluent stream from the reaction system, wherein theeffluent stream has an ethylene to propylene weight ratio of about fromabout 0.9:1.0 to about 2.2:1.0.
 29. The process of claim 28, wherein theethylene to propylene weight ratio is from about 1.1:1.0 to about1.4:1.0.
 30. The process of claim 28, wherein the process furthercomprises the step of: (e) removing a weight majority of the water fromthe mixed alcohol stream.
 31. The process of claim 28, wherein themolecular sieve catalyst composition comprises a molecular sieveselected from the group consisting of: SAPO-5, SAPO-8, SAPO-11, SAPO-16,SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37,SAPO-40, SAPO-41, SAPO-42, SAPO-44, SAPO-47, SAPO-56, AEI/CHAintergrowths, metal containing forms thereof, intergrown forms thereof,and mixtures thereof.
 32. The process of claim 28, wherein the methanolsynthesis catalyst is selected from the group consisting of: copperoxides, zinc oxides and aluminum oxides.
 33. The process of claim 28,wherein the process further comprises the step of: (e) removing lightends from at least a portion of the mixed alcohol stream, wherein thelight ends comprise carbon monoxide and hydrogen.
 34. The process ofclaim 28, wherein the process further comprises the step of: (e)contacting a natural gas stream with oxygen under conditions effectiveto convert the natural gas stream into the syngas stream.